diff --git a/src/messages/textDocument_completion.cc b/src/messages/textDocument_completion.cc
index 1fcfbd4a..5178e459 100644
--- a/src/messages/textDocument_completion.cc
+++ b/src/messages/textDocument_completion.cc
@@ -565,13 +565,14 @@ void MessageHandler::textDocument_completion(CompletionParam &param,
         if (!consumer->from_cache) {
           cache.withLock([&]() {
             cache.path = path;
+            cache.line = buffer_line;
             cache.position = begin_pos;
             cache.result = consumer->ls_items;
           });
         }
       };
 
-  if (cache.isCacheValid(path, begin_pos)) {
+  if (cache.isCacheValid(path, buffer_line, begin_pos)) {
     CompletionConsumer consumer(ccOpts, true);
     cache.withLock([&]() { consumer.ls_items = cache.result; });
     callback(&consumer);
diff --git a/src/messages/textDocument_signatureHelp.cc b/src/messages/textDocument_signatureHelp.cc
index bffdcf36..e5d5c0d7 100644
--- a/src/messages/textDocument_signatureHelp.cc
+++ b/src/messages/textDocument_signatureHelp.cc
@@ -151,6 +151,9 @@ void MessageHandler::textDocument_signatureHelp(
     reply.notOpened(path);
     return;
   }
+  std::string buffer_line;
+  if (param.position.line >= 0 && param.position.line < wf->buffer_lines.size())
+    buffer_line = wf->buffer_lines[param.position.line];
   {
     std::string filter;
     Position end_pos;
@@ -158,7 +161,7 @@ void MessageHandler::textDocument_signatureHelp(
   }
 
   SemaManager::OnComplete callback =
-      [reply, path, begin_pos](CodeCompleteConsumer *optConsumer) {
+      [reply, path, begin_pos, buffer_line](CodeCompleteConsumer *optConsumer) {
         if (!optConsumer)
           return;
         auto *consumer = static_cast<SignatureHelpConsumer *>(optConsumer);
@@ -166,6 +169,7 @@ void MessageHandler::textDocument_signatureHelp(
         if (!consumer->from_cache) {
           cache.withLock([&]() {
             cache.path = path;
+            cache.line = buffer_line;
             cache.position = begin_pos;
             cache.result = consumer->ls_sighelp;
           });
@@ -176,7 +180,7 @@ void MessageHandler::textDocument_signatureHelp(
   ccOpts.IncludeGlobals = false;
   ccOpts.IncludeMacros = false;
   ccOpts.IncludeBriefComments = true;
-  if (cache.isCacheValid(path, begin_pos)) {
+  if (cache.isCacheValid(path, buffer_line, begin_pos)) {
     SignatureHelpConsumer consumer(ccOpts, true);
     cache.withLock([&]() { consumer.ls_sighelp = cache.result; });
     callback(&consumer);
diff --git a/src/sema_manager.hh b/src/sema_manager.hh
index 2d3a969d..426ab7bb 100644
--- a/src/sema_manager.hh
+++ b/src/sema_manager.hh
@@ -164,6 +164,7 @@ struct SemaManager {
 template <typename T> struct CompleteConsumerCache {
   std::mutex mutex;
   std::string path;
+  std::string line;
   Position position;
   T result;
 
@@ -171,9 +172,12 @@ template <typename T> struct CompleteConsumerCache {
     std::lock_guard lock(mutex);
     fn();
   }
-  bool isCacheValid(const std::string path, Position position) {
+  bool isCacheValid(const std::string &path, const std::string &line,
+                    Position position) {
     std::lock_guard lock(mutex);
-    return this->path == path && this->position == position;
+    return this->position == position && this->path == path &&
+           this->line.compare(0, position.character, line, 0,
+                              position.character) == 0;
   }
 };
 } // namespace ccls