diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -192,6 +192,8 @@
   Fixes `Issue 56310 <https://github.com/llvm/llvm-project/issues/56310>`_.
 - Clang will now look through type sugar when checking a member function is a
   move assignment operator. Fixes `Issue 56456 <https://github.com/llvm/llvm-project/issues/56456>`_.
+- Fixed a crash when a variable with a bool enum type that has no definition
+  used in comparison operators. Fixes `Issue 56560 <https://github.com/llvm/llvm-project/issues/56560>`_.
 
 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -16209,7 +16209,10 @@
           ED->setIntegerTypeSourceInfo(TI);
         else
           ED->setIntegerType(QualType(EnumUnderlying.get<const Type *>(), 0));
-        ED->setPromotionType(ED->getIntegerType());
+        QualType EnumTy = ED->getIntegerType();
+        ED->setPromotionType(EnumTy->isPromotableIntegerType()
+                                 ? Context.getPromotedIntegerType(EnumTy)
+                                 : EnumTy);
       }
     } else { // struct/union
       New = RecordDecl::Create(Context, Kind, SearchDC, KWLoc, Loc, Name,
@@ -16831,8 +16834,11 @@
       if (TypeSourceInfo *TI = EnumUnderlying.dyn_cast<TypeSourceInfo*>())
         ED->setIntegerTypeSourceInfo(TI);
       else
-        ED->setIntegerType(QualType(EnumUnderlying.get<const Type*>(), 0));
-      ED->setPromotionType(ED->getIntegerType());
+        ED->setIntegerType(QualType(EnumUnderlying.get<const Type *>(), 0));
+      QualType EnumTy = ED->getIntegerType();
+      ED->setPromotionType(EnumTy->isPromotableIntegerType()
+                               ? Context.getPromotedIntegerType(EnumTy)
+                               : EnumTy);
       assert(ED->isComplete() && "enum with type should be complete");
     }
   } else {
diff --git a/clang/test/CXX/conv/conv.prom/p4.cpp b/clang/test/CXX/conv/conv.prom/p4.cpp
--- a/clang/test/CXX/conv/conv.prom/p4.cpp
+++ b/clang/test/CXX/conv/conv.prom/p4.cpp
@@ -26,3 +26,10 @@
   // FIXME: DR1407 will make this ill-formed
   e = +false_ // desired-error {{conversion from 'int' to 'bool'}}
 };
+
+namespace GH56560 {
+enum GH56560_1 : bool;
+bool GH56560_2(GH56560_1 a, GH56560_1 b) {
+    return a == b;
+}
+} // namespace GH56560