diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -13534,9 +13534,10 @@
     // Fall through for non-constants to give a sign conversion warning.
   }
 
-  if ((TargetRange.NonNegative && !LikelySourceRange.NonNegative) ||
-      (!TargetRange.NonNegative && LikelySourceRange.NonNegative &&
-       LikelySourceRange.Width == TargetRange.Width)) {
+  if ((!isa<EnumType>(Target) || !isa<EnumType>(Source)) &&
+      ((TargetRange.NonNegative && !LikelySourceRange.NonNegative) ||
+       (!TargetRange.NonNegative && LikelySourceRange.NonNegative &&
+        LikelySourceRange.Width == TargetRange.Width))) {
     if (S.SourceMgr.isInSystemMacro(CC))
       return;
 
diff --git a/clang/test/Sema/enum-enum-conversion.c b/clang/test/Sema/enum-enum-conversion.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Sema/enum-enum-conversion.c
@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -Wenum-conversion -verify %s
+// RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -fsyntax-only -Wconversion -verify %s
+
+// Signed enums
+enum SE1 { N1 = -1 };
+enum SE2 { N2 = -2 };
+// Unsigned unums
+enum UE1 { P1 };
+enum UE2 { P2 };
+
+enum UE2 f1(enum UE1 E) {
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum UE1' to different enumeration type 'enum UE2'}}
+}
+
+enum SE1 f2(enum UE1 E) {
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum UE1' to different enumeration type 'enum SE1'}}
+}
+
+enum UE1 f3(enum SE1 E) {
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum SE1' to different enumeration type 'enum UE1'}}
+}
+
+enum SE2 f4(enum SE1 E) {
+  return E; // expected-warning {{implicit conversion from enumeration type 'enum SE1' to different enumeration type 'enum SE2'}}
+}