Index: clang-tidy/readability/RedundantDeclarationCheck.cpp
===================================================================
--- clang-tidy/readability/RedundantDeclarationCheck.cpp
+++ clang-tidy/readability/RedundantDeclarationCheck.cpp
@@ -44,6 +44,10 @@
     if (VD->getPreviousDecl()->getStorageClass() == SC_Extern &&
         VD->getStorageClass() != SC_Extern)
       return;
+    // Don't warn about static member definition.
+    if (const DeclContext *DC = Prev->getLexicalDeclContext())
+      if (DC->getRedeclContext()->isRecord())
+        return;
     // Is this a multivariable declaration?
     for (const auto Other : VD->getDeclContext()->decls()) {
       if (Other != D && Other->getLocStart() == VD->getLocStart()) {
Index: test/clang-tidy/readability-redundant-declaration.cpp
===================================================================
--- test/clang-tidy/readability-redundant-declaration.cpp
+++ test/clang-tidy/readability-redundant-declaration.cpp
@@ -24,7 +24,13 @@
 
 // Original check crashed for the code below.
 namespace std {
-  typedef decltype(sizeof(0)) size_t;
+typedef decltype(sizeof(0)) size_t;
 }
-void* operator new(std::size_t) __attribute__((__externally_visible__));
-void* operator new[](std::size_t) __attribute__((__externally_visible__));
+void *operator new(std::size_t) __attribute__((__externally_visible__));
+void *operator new[](std::size_t) __attribute__((__externally_visible__));
+
+// Don't warn about static member definition.
+struct C {
+  static int I;
+};
+int C::I;