diff --git a/llvm/lib/MC/MCParser/AsmLexer.cpp b/llvm/lib/MC/MCParser/AsmLexer.cpp
--- a/llvm/lib/MC/MCParser/AsmLexer.cpp
+++ b/llvm/lib/MC/MCParser/AsmLexer.cpp
@@ -251,12 +251,12 @@
 }
 
 static void SkipIgnoredIntegerSuffix(const char *&CurPtr) {
-  // Skip ULL, UL, U, L and LL suffices.
-  if (CurPtr[0] == 'U')
+  // Skip case-insensitive ULL, UL, U, L and LL suffixes.
+  if (CurPtr[0] == 'U' || CurPtr[0] == 'u')
     ++CurPtr;
-  if (CurPtr[0] == 'L')
+  if (CurPtr[0] == 'L' || CurPtr[0] == 'l')
     ++CurPtr;
-  if (CurPtr[0] == 'L')
+  if (CurPtr[0] == 'L' || CurPtr[0] == 'l')
     ++CurPtr;
 }
 
diff --git a/llvm/test/MC/AsmParser/exprs.s b/llvm/test/MC/AsmParser/exprs.s
--- a/llvm/test/MC/AsmParser/exprs.s
+++ b/llvm/test/MC/AsmParser/exprs.s
@@ -18,6 +18,16 @@
         check_expr -1, ~0
         check_expr +1, 1
         check_expr 1 + 2, 3
+        check_expr 1U + 2U, 3U
+        check_expr 1L + 2L, 3L
+        check_expr 1UL + 2UL, 3UL
+        check_expr 1LL + 2L, 3LL
+        check_expr 1ULL + 2ULL, 3ULL
+        check_expr 1u + 2u, 3u
+        check_expr 1l + 2l, 3l
+        check_expr 1ul + 2ul, 3ul
+        check_expr 1ll + 2L, 3ll
+        check_expr 1ull + 2ull, 3ull
         check_expr 1 & 3, 1
         check_expr 4 / 2, 2
         check_expr 4 / -2, -2