diff --git a/src/cat.c b/src/cat.c
index 0574d2b..c577d2d 100644
--- a/src/cat.c
+++ b/src/cat.c
@@ -72,7 +72,7 @@ int main(int argc, char *argv[]) {
 				u = true;
 				break;
 			default:
-				printf("Usage: %s (-u) file...\n", argv[0]);
+				fprintf(stderr, "Usage: %s (-u) file...\n", argv[0]);
 				return EX_USAGE;
 		}
 	}
@@ -102,22 +102,22 @@ int main(int argc, char *argv[]) {
 		} else if ((file = fopen(argv[i], "r")) == NULL) {
 			switch (errno) {
 				case EACCES:
-					printf("%s: %s: Permission denied.\n", argv[0], argv[i]);
+					fprintf(stderr, "%s: %s: Permission denied.\n", argv[0], argv[i]);
 					return EX_NOINPUT;
 				case EISDIR:
-					printf("%s: %s: Is a directory.\n", argv[0], argv[i]);
+					fprintf(stderr, "%s: %s: Is a directory.\n", argv[0], argv[i]);
 					return EX_NOINPUT;
 				case ELOOP:
-					printf("%s: %s: Is a symbolic link loop.\n", argv[0], argv[i]);
+					fprintf(stderr, "%s: %s: Is a symbolic link loop.\n", argv[0], argv[i]);
 					return EX_UNAVAILABLE;
 				case EMFILE:
-					printf("%s: Internal error.\n", argv[0]);
+					fprintf(stderr, "%s: Internal error.\n", argv[0]);
 					return EX_SOFTWARE;
 				case ENOENT: case ENOTDIR: case ENXIO:
-					printf("%s: %s: No such file or directory.\n", argv[0], argv[i]);
+					fprintf(stderr, "%s: %s: No such file or directory.\n", argv[0], argv[i]);
 					return EX_NOINPUT;
 				default:
-					printf("%s: Unknown error.\n", argv[0]);
+					fprintf(stderr, "%s: Unknown error.\n", argv[0]);
 					return EX_UNAVAILABLE;
 			}
 		}