diff --git a/src/lake.c b/src/lake.c
index a9378fa..29ec540 100644
--- a/src/lake.c
+++ b/src/lake.c
@@ -68,7 +68,7 @@ char *lake_repr(LakeVal *expr)
         break;
     
     default:
-        printf("error: unrecognized value, type %d, size %zu bytes", expr->type, expr->size);
+        fprintf(stderr, "error: unrecognized value, type %d, size %zu bytes", expr->type, expr->size);
         s = g_strdup("");
     }
     
diff --git a/src/parse.c b/src/parse.c
index 5776b9a..31f22c0 100644
--- a/src/parse.c
+++ b/src/parse.c
@@ -43,7 +43,7 @@ static void warn_trailing(Ctx *ctx)
     /* don't warn about trailing comments */
     if (ctx->i < ctx->n && peek(ctx) != ';') {
         char *trailing = ctx->s + ctx->i;
-        printf("warning: ignoring %d trailing chars: %s\n", (int)(ctx->n - ctx->i), trailing);
+        fprintf(stderr, "warning: ignoring %d trailing chars: %s\n", (int)(ctx->n - ctx->i), trailing);
     }
 }
 
diff --git a/src/repl.c b/src/repl.c
index b9ab99a..c8bfb60 100644
--- a/src/repl.c
+++ b/src/repl.c
@@ -41,7 +41,7 @@ static LakeVal *prompt_read(LakeCtx *ctx, Env *env, char *prompt)
     char buf[n];
     if (!fgets(buf, n, stdin)) {
         if (ferror(stdin)) {
-            printf("error: cannot read from stdin");
+            fprintf(stderr, "error: cannot read from stdin");
         }
         if (feof(stdin)) {
             return VAL(EOF);
@@ -50,19 +50,19 @@ static LakeVal *prompt_read(LakeCtx *ctx, Env *env, char *prompt)
     }
 	/* trim the newline if any */
 	buf[strcspn(buf, "\n")] = '\0';
-	
+
 	/* parse list expressions */
 	if (first_char(buf) == '(') {
         return parse_expr(ctx, buf, strlen(buf));
     }
-    
+
     /* try to parse a naked call without parens
        (makes the repl more palatable) */
     LakeList *list = parse_naked_list(ctx, buf, strlen(buf));
     if (!list || LIST_N(list) == 0) return NULL;
 
     LakeVal *result;
-    
+
     /* naked call */
     LakeVal *head;
     if (is_special_form(ctx, list) ||
@@ -75,7 +75,7 @@ static LakeVal *prompt_read(LakeCtx *ctx, Env *env, char *prompt)
     else {
         result = LIST_VAL(list, 0);
     }
-    
+
     return result;
 }