diff --git a/mlir/test/CAPI/ir.c b/mlir/test/CAPI/ir.c
--- a/mlir/test/CAPI/ir.c
+++ b/mlir/test/CAPI/ir.c
@@ -21,6 +21,7 @@
 #include "mlir-c/Registration.h"
 
 #include <assert.h>
+#include <inttypes.h>
 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -1597,7 +1598,7 @@
 
   // Test operand APIs.
   intptr_t numOperands = mlirOperationGetNumOperands(op);
-  fprintf(stderr, "Num Operands: %ld\n", numOperands);
+  fprintf(stderr, "Num Operands: %" PRIdPTR "\n", numOperands);
   // CHECK: Num Operands: 1
 
   MlirValue opOperand = mlirOperationGetOperand(op, 0);
@@ -1653,19 +1654,22 @@
 
 // Wraps a diagnostic into additional text we can match against.
 MlirLogicalResult errorHandler(MlirDiagnostic diagnostic, void *userData) {
-  fprintf(stderr, "processing diagnostic (userData: %ld) <<\n", (long)userData);
+  fprintf(stderr, "processing diagnostic (userData: %" PRIdPTR ") <<\n",
+          (intptr_t)userData);
   mlirDiagnosticPrint(diagnostic, printToStderr, NULL);
   fprintf(stderr, "\n");
   MlirLocation loc = mlirDiagnosticGetLocation(diagnostic);
   mlirLocationPrint(loc, printToStderr, NULL);
   assert(mlirDiagnosticGetNumNotes(diagnostic) == 0);
-  fprintf(stderr, "\n>> end of diagnostic (userData: %ld)\n", (long)userData);
+  fprintf(stderr, "\n>> end of diagnostic (userData: %" PRIdPTR ")\n",
+          (intptr_t)userData);
   return mlirLogicalResultSuccess();
 }
 
 // Logs when the delete user data callback is called
 static void deleteUserData(void *userData) {
-  fprintf(stderr, "deleting user data (userData: %ld)\n", (long)userData);
+  fprintf(stderr, "deleting user data (userData: %" PRIdPTR ")\n",
+          (intptr_t)userData);
 }
 
 void testDiagnostics() {