diff --git a/src/cargo/util/toml/mod.rs b/src/cargo/util/toml/mod.rs
index fa0362843..22447668f 100644
--- a/src/cargo/util/toml/mod.rs
+++ b/src/cargo/util/toml/mod.rs
@@ -2061,7 +2061,7 @@ impl TomlTarget {
         if self.proc_macro_raw.is_some() && self.proc_macro_raw2.is_some() {
             warnings.push(format!(
                 "found both `proc-macro` and `proc_macro` are set \
-                 in the `{}` library",
+                 in the `{}` library target",
                 self.name()
             ));
         }
@@ -2078,6 +2078,17 @@ impl TomlTarget {
         })
     }
 
+    fn validate_crate_types(&self, target_kind_human: &str, warnings: &mut Vec<String>) {
+        if self.crate_type.is_some() && self.crate_type2.is_some() {
+            warnings.push(format!(
+                "found both `crate-type` and `crate_type` are set \
+                 in the `{}` {} target",
+                self.name(),
+                target_kind_human
+            ));
+        }
+    }
+
     fn crate_types(&self) -> Option<&Vec<String>> {
         self.crate_type
             .as_ref()
diff --git a/src/cargo/util/toml/targets.rs b/src/cargo/util/toml/targets.rs
index 08acb0286..ac9bf468a 100644
--- a/src/cargo/util/toml/targets.rs
+++ b/src/cargo/util/toml/targets.rs
@@ -175,6 +175,7 @@ fn clean_lib(
         None => return Ok(None),
     };
     lib.validate_proc_macro(warnings);
+    lib.validate_crate_types("library", warnings);
 
     validate_target_name(lib, "library", "lib", warnings)?;
 
@@ -399,6 +400,7 @@ fn clean_examples(
 
     let mut result = Vec::new();
     for (path, toml) in targets {
+        toml.validate_crate_types("example", warnings);
         let crate_types = match toml.crate_types() {
             Some(kinds) => kinds.iter().map(|s| s.into()).collect(),
             None => Vec::new(),
diff --git a/tests/testsuite/build.rs b/tests/testsuite/build.rs
index 70550431a..43eb3ec8e 100644
--- a/tests/testsuite/build.rs
+++ b/tests/testsuite/build.rs
@@ -1676,6 +1676,78 @@ Caused by:
         .run();
 }
 
+#[cargo_test]
+fn lib_crate_types_conflicting_warning() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [project]
+                name = "foo"
+                version = "0.5.0"
+                authors = ["wycats@example.com"]
+
+                [lib]
+                name = "foo"
+                crate-type = ["rlib", "dylib"]
+                crate_type = ["staticlib", "dylib"]
+            "#,
+        )
+        .file("src/lib.rs", "pub fn foo() {}")
+        .build();
+    p.cargo("build")
+    .with_stderr_contains(
+        "[WARNING] found both `crate-type` and `crate_type` are set in the `foo` library target",
+    )
+        .run();
+}
+
+#[cargo_test]
+fn examples_crate_types_conflicting_warning() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [project]
+                name = "foo"
+                version = "0.5.0"
+                authors = ["wycats@example.com"]
+
+                [[example]]
+                name = "ex"
+                path = "examples/ex.rs"
+                crate-type = ["rlib", "dylib"]
+                crate_type = ["proc_macro"]
+                [[example]]
+                name = "goodbye"
+                path = "examples/ex-goodbye.rs"
+                crate-type = ["rlib", "dylib"]
+                crate_type = ["rlib", "staticlib"]
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .file(
+            "examples/ex.rs",
+            r#"
+                fn main() { println!("ex"); }
+            "#,
+        )
+        .file(
+            "examples/ex-goodbye.rs",
+            r#"
+                fn main() { println!("goodbye"); }
+            "#,
+        )
+        .build();
+    p.cargo("build")
+        .with_stderr_contains(
+            "\
+[WARNING] found both `crate-type` and `crate_type` are set in the `ex` example target
+[WARNING] found both `crate-type` and `crate_type` are set in the `goodbye` example target",
+        )
+        .run();
+}
+
 #[cargo_test]
 fn self_dependency() {
     let p = project()
diff --git a/tests/testsuite/proc_macro.rs b/tests/testsuite/proc_macro.rs
index 2d2f784c9..c40d6a153 100644
--- a/tests/testsuite/proc_macro.rs
+++ b/tests/testsuite/proc_macro.rs
@@ -406,7 +406,7 @@ fn proc_macro_conflicting_warning() {
 
     foo.cargo("build")
         .with_stderr_contains(
-            "[WARNING] found both `proc-macro` and `proc_macro` are set in the `foo` library",
+            "[WARNING] found both `proc-macro` and `proc_macro` are set in the `foo` library target",
         )
         .run();
 }