diff --git a/src/cargo/util/toml/mod.rs b/src/cargo/util/toml/mod.rs
index 1c95e50fa89..dc6e3855901 100644
--- a/src/cargo/util/toml/mod.rs
+++ b/src/cargo/util/toml/mod.rs
@@ -1734,12 +1734,11 @@ impl<P: ResolveToPath> DetailedTomlDependency<P> {
 
             for &(key, key_name) in &git_only_keys {
                 if key.is_some() {
-                    let msg = format!(
-                        "key `{}` is ignored for dependency ({}). \
-                         This will be considered an error in future versions",
-                        key_name, name_in_toml
+                    bail!(
+                        "key `{}` is ignored for dependency ({}).",
+                        key_name,
+                        name_in_toml
                     );
-                    cx.warnings.push(msg)
                 }
             }
         }
@@ -1791,13 +1790,11 @@ impl<P: ResolveToPath> DetailedTomlDependency<P> {
             ),
             (Some(git), maybe_path, _, _) => {
                 if maybe_path.is_some() {
-                    let msg = format!(
+                    bail!(
                         "dependency ({}) specification is ambiguous. \
-                         Only one of `git` or `path` is allowed. \
-                         This will be considered an error in future versions",
+                         Only one of `git` or `path` is allowed.",
                         name_in_toml
                     );
-                    cx.warnings.push(msg)
                 }
 
                 let n_details = [&self.branch, &self.tag, &self.rev]
diff --git a/tests/testsuite/bad_config.rs b/tests/testsuite/bad_config.rs
index c9a2f6e11c6..05f755a2ecb 100644
--- a/tests/testsuite/bad_config.rs
+++ b/tests/testsuite/bad_config.rs
@@ -1112,11 +1112,12 @@ fn both_git_and_path_specified() {
 
     foo.cargo("build -v")
         .with_status(101)
-        .with_stderr_contains(
+        .with_stderr(
             "\
-[WARNING] dependency (bar) specification is ambiguous. \
-Only one of `git` or `path` is allowed. \
-This will be considered an error in future versions
+error: failed to parse manifest at `[..]`
+
+Caused by:
+  dependency (bar) specification is ambiguous. Only one of `git` or `path` is allowed.
 ",
         )
         .run();
@@ -1182,9 +1183,13 @@ fn ignored_git_revision() {
 
     foo.cargo("build -v")
         .with_status(101)
-        .with_stderr_contains(
-            "[WARNING] key `branch` is ignored for dependency (bar). \
-             This will be considered an error in future versions",
+        .with_stderr(
+            "\
+error: failed to parse manifest at `[..]`
+
+Caused by:
+  key `branch` is ignored for dependency (bar).
+",
         )
         .run();
 }