diff --git a/src/cargo/core/compiler/mod.rs b/src/cargo/core/compiler/mod.rs
index 22f70bf67aa..32f79947843 100644
--- a/src/cargo/core/compiler/mod.rs
+++ b/src/cargo/core/compiler/mod.rs
@@ -23,7 +23,7 @@ use same_file::is_same_file;
 use serde::Serialize;
 
 use crate::core::manifest::TargetSourcePath;
-use crate::core::profiles::{Lto, Profile};
+use crate::core::profiles::{Lto, PanicStrategy, Profile};
 use crate::core::{PackageId, Target};
 use crate::util::errors::{CargoResult, CargoResultExt, Internal, ProcessError};
 use crate::util::paths;
@@ -794,7 +794,7 @@ fn build_base_args<'a, 'cfg>(
         cmd.arg("-C").arg(&format!("opt-level={}", opt_level));
     }
 
-    if let Some(panic) = panic.as_ref() {
+    if *panic != PanicStrategy::Unwind {
         cmd.arg("-C").arg(format!("panic={}", panic));
     }
 
diff --git a/src/cargo/core/profiles.rs b/src/cargo/core/profiles.rs
index 18355b9b40e..be97a54ef15 100644
--- a/src/cargo/core/profiles.rs
+++ b/src/cargo/core/profiles.rs
@@ -111,8 +111,8 @@ impl Profiles {
         let mut profile = maker.get_profile(Some(pkg_id), is_member, unit_for);
         // `panic` should not be set for tests/benches, or any of their
         // dependencies.
-        if !unit_for.is_panic_ok() || mode.is_any_test() {
-            profile.panic = None;
+        if !unit_for.is_panic_abort_ok() || mode.is_any_test() {
+            profile.panic = PanicStrategy::Unwind;
         }
 
         // Incremental can be globally overridden.
@@ -390,8 +390,13 @@ fn merge_profile(profile: &mut Profile, toml: &TomlProfile) {
     if let Some(rpath) = toml.rpath {
         profile.rpath = rpath;
     }
-    if let Some(ref panic) = toml.panic {
-        profile.panic = Some(InternedString::new(panic));
+    if let Some(panic) = &toml.panic {
+        profile.panic = match panic.as_str() {
+            "unwind" => PanicStrategy::Unwind,
+            "abort" => PanicStrategy::Abort,
+            // This should be validated in TomlProfile::validate
+            _ => panic!("Unexpected panic setting `{}`", panic),
+        };
     }
     if let Some(overflow_checks) = toml.overflow_checks {
         profile.overflow_checks = overflow_checks;
@@ -415,7 +420,7 @@ pub struct Profile {
     pub overflow_checks: bool,
     pub rpath: bool,
     pub incremental: bool,
-    pub panic: Option<InternedString>,
+    pub panic: PanicStrategy,
 }
 
 impl Default for Profile {
@@ -430,7 +435,7 @@ impl Default for Profile {
             overflow_checks: false,
             rpath: false,
             incremental: false,
-            panic: None,
+            panic: PanicStrategy::Unwind,
         }
     }
 }
@@ -530,26 +535,26 @@ impl Profile {
     fn comparable(
         &self,
     ) -> (
-        &InternedString,
-        &Lto,
-        &Option<u32>,
-        &Option<u32>,
-        &bool,
-        &bool,
-        &bool,
-        &bool,
-        &Option<InternedString>,
+        InternedString,
+        Lto,
+        Option<u32>,
+        Option<u32>,
+        bool,
+        bool,
+        bool,
+        bool,
+        PanicStrategy,
     ) {
         (
-            &self.opt_level,
-            &self.lto,
-            &self.codegen_units,
-            &self.debuginfo,
-            &self.debug_assertions,
-            &self.overflow_checks,
-            &self.rpath,
-            &self.incremental,
-            &self.panic,
+            self.opt_level,
+            self.lto,
+            self.codegen_units,
+            self.debuginfo,
+            self.debug_assertions,
+            self.overflow_checks,
+            self.rpath,
+            self.incremental,
+            self.panic,
         )
     }
 }
@@ -564,6 +569,23 @@ pub enum Lto {
     Named(InternedString),
 }
 
+/// The `panic` setting.
+#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash, PartialOrd, Ord)]
+pub enum PanicStrategy {
+    Unwind,
+    Abort,
+}
+
+impl fmt::Display for PanicStrategy {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            PanicStrategy::Unwind => "unwind",
+            PanicStrategy::Abort => "abort",
+        }
+        .fmt(f)
+    }
+}
+
 /// Flags used in creating `Unit`s to indicate the purpose for the target, and
 /// to ensure the target's dependencies have the correct settings.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
@@ -571,11 +593,11 @@ pub struct UnitFor {
     /// A target for `build.rs` or any of its dependencies. This enables
     /// `build-override` profiles for these targets.
     custom_build: bool,
-    /// This is true if it is *allowed* to set the `panic` flag. Currently
+    /// This is true if it is *allowed* to set the `panic=abort` flag. Currently
     /// this is false for test/bench targets and all their dependencies, and
     /// "for_host" units such as proc macro and custom build scripts and their
     /// dependencies.
-    panic_ok: bool,
+    panic_abort_ok: bool,
 }
 
 impl UnitFor {
@@ -584,7 +606,7 @@ impl UnitFor {
     pub fn new_normal() -> UnitFor {
         UnitFor {
             custom_build: false,
-            panic_ok: true,
+            panic_abort_ok: true,
         }
     }
 
@@ -592,7 +614,7 @@ impl UnitFor {
     pub fn new_build() -> UnitFor {
         UnitFor {
             custom_build: true,
-            panic_ok: false,
+            panic_abort_ok: false,
         }
     }
 
@@ -600,7 +622,7 @@ impl UnitFor {
     pub fn new_compiler() -> UnitFor {
         UnitFor {
             custom_build: false,
-            panic_ok: false,
+            panic_abort_ok: false,
         }
     }
 
@@ -608,18 +630,18 @@ impl UnitFor {
     pub fn new_test() -> UnitFor {
         UnitFor {
             custom_build: false,
-            panic_ok: false,
+            panic_abort_ok: false,
         }
     }
 
     /// Creates a variant based on `for_host` setting.
     ///
-    /// When `for_host` is true, this clears `panic_ok` in a sticky fashion so
-    /// that all its dependencies also have `panic_ok=false`.
+    /// When `for_host` is true, this clears `panic_abort_ok` in a sticky fashion so
+    /// that all its dependencies also have `panic_abort_ok=false`.
     pub fn with_for_host(self, for_host: bool) -> UnitFor {
         UnitFor {
             custom_build: self.custom_build,
-            panic_ok: self.panic_ok && !for_host,
+            panic_abort_ok: self.panic_abort_ok && !for_host,
         }
     }
 
@@ -630,8 +652,8 @@ impl UnitFor {
     }
 
     /// Returns `true` if this unit is allowed to set the `panic` compiler flag.
-    pub fn is_panic_ok(self) -> bool {
-        self.panic_ok
+    pub fn is_panic_abort_ok(self) -> bool {
+        self.panic_abort_ok
     }
 
     /// All possible values, used by `clean`.
@@ -639,15 +661,15 @@ impl UnitFor {
         static ALL: [UnitFor; 3] = [
             UnitFor {
                 custom_build: false,
-                panic_ok: true,
+                panic_abort_ok: true,
             },
             UnitFor {
                 custom_build: true,
-                panic_ok: false,
+                panic_abort_ok: false,
             },
             UnitFor {
                 custom_build: false,
-                panic_ok: false,
+                panic_abort_ok: false,
             },
         ];
         &ALL
diff --git a/src/cargo/util/toml/mod.rs b/src/cargo/util/toml/mod.rs
index 31099a78e81..a3d53d962d8 100644
--- a/src/cargo/util/toml/mod.rs
+++ b/src/cargo/util/toml/mod.rs
@@ -5,6 +5,7 @@ use std::path::{Path, PathBuf};
 use std::rc::Rc;
 use std::str;
 
+use failure::bail;
 use log::{debug, trace};
 use semver::{self, VersionReq};
 use serde::de;
@@ -52,8 +53,9 @@ fn do_read_manifest(
     let package_root = manifest_file.parent().unwrap();
 
     let toml = {
-        let pretty_filename =
-            manifest_file.strip_prefix(config.cwd()).unwrap_or(manifest_file);
+        let pretty_filename = manifest_file
+            .strip_prefix(config.cwd())
+            .unwrap_or(manifest_file);
         parse(contents, pretty_filename, config)?
     };
 
@@ -78,7 +80,7 @@ fn do_read_manifest(
             TomlManifest::to_real_manifest(&manifest, source_id, package_root, config)?;
         add_unused(manifest.warnings_mut());
         if !manifest.targets().iter().any(|t| !t.is_custom_build()) {
-            failure::bail!(
+            bail!(
                 "no targets specified in the manifest\n  \
                  either src/lib.rs, src/main.rs, a [lib] section, or \
                  [[bin]] section must be present"
@@ -471,7 +473,7 @@ impl TomlProfile {
             "dev" | "release" => {}
             _ => {
                 if self.overrides.is_some() || self.build_override.is_some() {
-                    failure::bail!(
+                    bail!(
                         "Profile overrides may only be specified for \
                          `dev` or `release` profile, not `{}`.",
                         name
@@ -491,21 +493,31 @@ impl TomlProfile {
             }
             _ => {}
         }
+
+        if let Some(panic) = &self.panic {
+            if panic != "unwind" && panic != "abort" {
+                bail!(
+                    "`panic` setting of `{}` is not a valid setting,\
+                     must be `unwind` or `abort`",
+                    panic
+                );
+            }
+        }
         Ok(())
     }
 
     fn validate_override(&self) -> CargoResult<()> {
         if self.overrides.is_some() || self.build_override.is_some() {
-            failure::bail!("Profile overrides cannot be nested.");
+            bail!("Profile overrides cannot be nested.");
         }
         if self.panic.is_some() {
-            failure::bail!("`panic` may not be specified in a profile override.")
+            bail!("`panic` may not be specified in a profile override.")
         }
         if self.lto.is_some() {
-            failure::bail!("`lto` may not be specified in a profile override.")
+            bail!("`lto` may not be specified in a profile override.")
         }
         if self.rpath.is_some() {
-            failure::bail!("`rpath` may not be specified in a profile override.")
+            bail!("`rpath` may not be specified in a profile override.")
         }
         Ok(())
     }
@@ -830,7 +842,7 @@ impl TomlManifest {
 
         let package_name = project.name.trim();
         if package_name.is_empty() {
-            failure::bail!("package name cannot be an empty string")
+            bail!("package name cannot be an empty string")
         }
 
         validate_package_name(package_name, "package name", "")?;
@@ -951,7 +963,7 @@ impl TomlManifest {
                 let name = dep.name_in_toml();
                 let prev = names_sources.insert(name.to_string(), dep.source_id());
                 if prev.is_some() && prev != Some(dep.source_id()) {
-                    failure::bail!(
+                    bail!(
                         "Dependency '{}' has different source paths depending on the build \
                          target. Each dependency must have a single canonical source path \
                          irrespective of build target.",
@@ -1006,7 +1018,7 @@ impl TomlManifest {
             (None, root) => WorkspaceConfig::Member {
                 root: root.cloned(),
             },
-            (Some(..), Some(..)) => failure::bail!(
+            (Some(..), Some(..)) => bail!(
                 "cannot configure both `package.workspace` and \
                  `[workspace]`, only one can be specified"
             ),
@@ -1082,43 +1094,43 @@ impl TomlManifest {
         config: &Config,
     ) -> CargoResult<(VirtualManifest, Vec<PathBuf>)> {
         if me.project.is_some() {
-            failure::bail!("virtual manifests do not define [project]");
+            bail!("virtual manifests do not define [project]");
         }
         if me.package.is_some() {
-            failure::bail!("virtual manifests do not define [package]");
+            bail!("virtual manifests do not define [package]");
         }
         if me.lib.is_some() {
-            failure::bail!("virtual manifests do not specify [lib]");
+            bail!("virtual manifests do not specify [lib]");
         }
         if me.bin.is_some() {
-            failure::bail!("virtual manifests do not specify [[bin]]");
+            bail!("virtual manifests do not specify [[bin]]");
         }
         if me.example.is_some() {
-            failure::bail!("virtual manifests do not specify [[example]]");
+            bail!("virtual manifests do not specify [[example]]");
         }
         if me.test.is_some() {
-            failure::bail!("virtual manifests do not specify [[test]]");
+            bail!("virtual manifests do not specify [[test]]");
         }
         if me.bench.is_some() {
-            failure::bail!("virtual manifests do not specify [[bench]]");
+            bail!("virtual manifests do not specify [[bench]]");
         }
         if me.dependencies.is_some() {
-            failure::bail!("virtual manifests do not specify [dependencies]");
+            bail!("virtual manifests do not specify [dependencies]");
         }
         if me.dev_dependencies.is_some() || me.dev_dependencies2.is_some() {
-            failure::bail!("virtual manifests do not specify [dev-dependencies]");
+            bail!("virtual manifests do not specify [dev-dependencies]");
         }
         if me.build_dependencies.is_some() || me.build_dependencies2.is_some() {
-            failure::bail!("virtual manifests do not specify [build-dependencies]");
+            bail!("virtual manifests do not specify [build-dependencies]");
         }
         if me.features.is_some() {
-            failure::bail!("virtual manifests do not specify [features]");
+            bail!("virtual manifests do not specify [features]");
         }
         if me.target.is_some() {
-            failure::bail!("virtual manifests do not specify [target]");
+            bail!("virtual manifests do not specify [target]");
         }
         if me.badges.is_some() {
-            failure::bail!("virtual manifests do not specify [badges]");
+            bail!("virtual manifests do not specify [badges]");
         }
 
         let mut nested_paths = Vec::new();
@@ -1151,7 +1163,7 @@ impl TomlManifest {
                 &config.exclude,
             )),
             None => {
-                failure::bail!("virtual manifests must be configured with [workspace]");
+                bail!("virtual manifests must be configured with [workspace]");
             }
         };
         Ok((
@@ -1162,7 +1174,7 @@ impl TomlManifest {
 
     fn replace(&self, cx: &mut Context<'_, '_>) -> CargoResult<Vec<(PackageIdSpec, Dependency)>> {
         if self.patch.is_some() && self.replace.is_some() {
-            failure::bail!("cannot specify both [replace] and [patch]");
+            bail!("cannot specify both [replace] and [patch]");
         }
         let mut replace = Vec::new();
         for (spec, replacement) in self.replace.iter().flat_map(|x| x) {
@@ -1182,7 +1194,7 @@ impl TomlManifest {
                 TomlDependency::Simple(..) => true,
             };
             if version_specified {
-                failure::bail!(
+                bail!(
                     "replacements cannot specify a version \
                      requirement, but found one for `{}`",
                     spec
@@ -1331,12 +1343,12 @@ impl DetailedTomlDependency {
             self.registry.as_ref(),
             self.registry_index.as_ref(),
         ) {
-            (Some(_), _, Some(_), _) | (Some(_), _, _, Some(_)) => failure::bail!(
+            (Some(_), _, Some(_), _) | (Some(_), _, _, Some(_)) => bail!(
                 "dependency ({}) specification is ambiguous. \
                  Only one of `git` or `registry` is allowed.",
                 name_in_toml
             ),
-            (_, _, Some(_), Some(_)) => failure::bail!(
+            (_, _, Some(_), Some(_)) => bail!(
                 "dependency ({}) specification is ambiguous. \
                  Only one of `registry` or `registry-index` is allowed.",
                 name_in_toml
diff --git a/tests/testsuite/profiles.rs b/tests/testsuite/profiles.rs
index 97815c395b6..21510f3833e 100644
--- a/tests/testsuite/profiles.rs
+++ b/tests/testsuite/profiles.rs
@@ -376,3 +376,40 @@ fn profile_doc_deprecated() {
         .with_stderr_contains("[WARNING] profile `doc` is deprecated and has no effect")
         .run();
 }
+
+#[test]
+fn panic_unwind_does_not_build_twice() {
+    // Check for a bug where `lib` was built twice, once with panic set and
+    // once without. Since "unwind" is the default, they are the same and
+    // should only be built once.
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+            name = "foo"
+            version = "0.1.0"
+
+            [profile.dev]
+            panic = "unwind"
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .file("src/main.rs", "fn main() {}")
+        .file("tests/t1.rs", "")
+        .build();
+
+    p.cargo("test -v --tests --no-run")
+        .with_stderr_unordered(
+            "\
+[COMPILING] foo [..]
+[RUNNING] `rustc --crate-name foo src/lib.rs [..]--crate-type lib [..]
+[RUNNING] `rustc --crate-name foo src/lib.rs [..] --test [..]
+[RUNNING] `rustc --crate-name foo src/main.rs [..]--crate-type bin [..]
+[RUNNING] `rustc --crate-name foo src/main.rs [..] --test [..]
+[RUNNING] `rustc --crate-name t1 tests/t1.rs [..]
+[FINISHED] [..]
+",
+        )
+        .run();
+}