diff --git a/test/Transforms/SimplifyLibCalls/IsDigit.ll b/test/Transforms/SimplifyLibCalls/IsDigit.ll
new file mode 100644
index 00000000000..1f8f7cf548a
--- /dev/null
+++ b/test/Transforms/SimplifyLibCalls/IsDigit.ll
@@ -0,0 +1,17 @@
+; Test that the IsDigitOptimizer works correctly
+; RUN: llvm-as < %s | opt -simplify-libcalls | llvm-dis | not grep 'call.*isdigit' 
+
+declare int %isdigit(int)
+
+implementation   ; Functions:
+
+int %main () {
+  %val1 = call int %isdigit(int 47)
+  %val2 = call int %isdigit(int 48)
+  %val3 = call int %isdigit(int 57)
+  %val4 = call int %isdigit(int 58)
+  %rslt1 = add int %val1, %val2
+  %rslt2 = add int %val3, %val4
+  %rslt = add int %rslt1, %rslt2
+  ret int %rslt
+}