diff --git a/sections/cper-section-arm.c b/sections/cper-section-arm.c
index d360d18..35d0ef3 100644
--- a/sections/cper-section-arm.c
+++ b/sections/cper-section-arm.c
@@ -114,7 +114,7 @@
 		char *node_desc_str = malloc(EFI_ERROR_DESCRIPTION_STRING_LEN);
 		outstr_len = snprintf(node_desc_str,
 				      EFI_ERROR_DESCRIPTION_STRING_LEN,
-				      " on CPU %ld", sock);
+				      " on CPU %lu", sock);
 		if (outstr_len < 0) {
 			cper_print_log(
 				"Error: Could not write to node description string\n");