Index: clang-tools-extra/trunk/clang-tidy/fuchsia/MultipleInheritanceCheck.cpp
===================================================================
--- clang-tools-extra/trunk/clang-tidy/fuchsia/MultipleInheritanceCheck.cpp
+++ clang-tools-extra/trunk/clang-tidy/fuchsia/MultipleInheritanceCheck.cpp
@@ -93,7 +93,8 @@
     return;
 
   // Match declarations which have bases.
-  Finder->addMatcher(cxxRecordDecl(hasBases()).bind("decl"), this);
+  Finder->addMatcher(
+      cxxRecordDecl(allOf(hasBases(), isDefinition())).bind("decl"), this);
 }
 
 void MultipleInheritanceCheck::check(const MatchFinder::MatchResult &Result) {
Index: clang-tools-extra/trunk/test/clang-tidy/fuchsia-multiple-inheritance.cpp
===================================================================
--- clang-tools-extra/trunk/test/clang-tidy/fuchsia-multiple-inheritance.cpp
+++ clang-tools-extra/trunk/test/clang-tidy/fuchsia-multiple-inheritance.cpp
@@ -41,6 +41,9 @@
   virtual int baz() = 0;
 };
 
+// Shouldn't warn on forward declarations.
+class Bad_Child1;
+
 // Inherits from multiple concrete classes.
 // CHECK-MESSAGES: [[@LINE+2]]:1: warning: inheriting mulitple classes that aren't pure virtual is discouraged [fuchsia-multiple-inheritance]
 // CHECK-NEXT: class Bad_Child1 : public Base_A, Base_B {};