diff --git a/cputree.c b/cputree.c
index d09af43..e2541aa 100644
--- a/cputree.c
+++ b/cputree.c
@@ -361,9 +361,14 @@ static void do_one_cpu(char *path)
 			entry = readdir(dir);
 			if (!entry)
 				break;
-			if (strstr(entry->d_name, "node")) {
-				nodeid = strtoul(&entry->d_name[4], NULL, 10);
-				break;
+			if (strncmp(entry->d_name, "node", 4) == 0) {
+				char *end;
+				int num;
+				num = strtol(entry->d_name + 4, &end, 10);
+				if (!*end && num >= 0) {
+					nodeid = num;
+					break;
+				}
 			}
 		} while (entry);
 		closedir(dir);
diff --git a/numa.c b/numa.c
index cd67ec8..f0b1a98 100644
--- a/numa.c
+++ b/numa.c
@@ -29,6 +29,7 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <ctype.h>
 #include <sys/types.h>
 #include <dirent.h>
 
@@ -115,7 +116,9 @@ void build_numa_node_list(void)
 		entry = readdir(dir);
 		if (!entry)
 			break;
-		if ((entry->d_type == DT_DIR) && (strstr(entry->d_name, "node"))) {
+		if ((entry->d_type == DT_DIR) &&
+		    (strncmp(entry->d_name, "node", 4) == 0) &&
+		    isdigit(entry->d_name[4])) {
 			add_one_node(entry->d_name);
 		}
 	} while (entry);