diff --git a/c++/src/kj/filesystem.c++ b/c++/src/kj/filesystem.c++
index 01bab169d8..9b7a05a913 100644
--- a/c++/src/kj/filesystem.c++
+++ b/c++/src/kj/filesystem.c++
@@ -1511,7 +1511,7 @@ private:
               entry.set(kj::mv(copy));
             } else {
               if (mode == TransferMode::MOVE) {
-                KJ_ASSERT(fromDirectory.tryRemove(fromPath), "could't move node", fromPath) {
+                KJ_ASSERT(fromDirectory.tryRemove(fromPath), "couldn't move node", fromPath) {
                   return false;
                 }
               }
@@ -1543,7 +1543,7 @@ private:
               entry.set(kj::mv(copy));
             } else {
               if (mode == TransferMode::MOVE) {
-                KJ_ASSERT(fromDirectory.tryRemove(fromPath), "could't move node", fromPath) {
+                KJ_ASSERT(fromDirectory.tryRemove(fromPath), "couldn't move node", fromPath) {
                   return false;
                 }
               }
@@ -1560,7 +1560,7 @@ private:
             // Since symlinks are immutable, we can implement LINK the same as COPY.
             entry.init(SymlinkNode { lastModified.orDefault(clock.now()), kj::mv(*content) });
             if (mode == TransferMode::MOVE) {
-              KJ_ASSERT(fromDirectory.tryRemove(fromPath), "could't move node", fromPath) {
+              KJ_ASSERT(fromDirectory.tryRemove(fromPath), "couldn't move node", fromPath) {
                 return false;
               }
             }