diff --git a/llvm/include/llvm/ADT/APFloat.h b/llvm/include/llvm/ADT/APFloat.h
index 97547fb577e0e..436052d8aa265 100644
--- a/llvm/include/llvm/ADT/APFloat.h
+++ b/llvm/include/llvm/ADT/APFloat.h
@@ -1474,11 +1474,11 @@ class APFloat : public APFloatBase {
   friend APFloat frexp(const APFloat &X, int &Exp, roundingMode RM);
   friend IEEEFloat;
   friend DoubleAPFloat;
+  // Since Storage is private, friend class APFloatEBOChecker is added to allow
+  // access to it in APFloat.cpp.
+  friend class APFloatEBOChecker;
 };
 
-static_assert(sizeof(APFloat) == sizeof(detail::IEEEFloat),
-              "Empty base class optimization is not performed.");
-
 /// See friend declarations above.
 ///
 /// These additional declarations are required in order to compile LLVM with IBM
diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index a33b6c4a6ddc6..f48c82b6afdd8 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -99,6 +99,11 @@ enum class fltNanEncoding {
   NegativeZero,
 };
 
+class APFloatEBOChecker {
+  static_assert(sizeof(APFloat) == sizeof(APFloat::U),
+                "Empty base class optimization is not performed.");
+};
+
 /* Represents floating point arithmetic semantics.  */
 struct fltSemantics {
   /* The largest E such that 2^E is representable; this matches the