diff --git a/plugins/clang/duchain/parsesession.h b/plugins/clang/duchain/parsesession.h
--- a/plugins/clang/duchain/parsesession.h
+++ b/plugins/clang/duchain/parsesession.h
@@ -79,6 +79,8 @@
     /// TODO: share this file for all TUs that use the same defines (probably most in a project)
     ///       best would be a PCH, if possible
     QTemporaryFile m_definesFile;
+    // cached ProblemPointer representation for diagnostics
+    QVector<KDevelop::ProblemPointer> m_diagnosticsCache;
 };
 
 /**
diff --git a/plugins/clang/duchain/parsesession.cpp b/plugins/clang/duchain/parsesession.cpp
--- a/plugins/clang/duchain/parsesession.cpp
+++ b/plugins/clang/duchain/parsesession.cpp
@@ -380,6 +380,7 @@
 void ParseSessionData::setUnit(CXTranslationUnit unit)
 {
     m_unit = unit;
+    m_diagnosticsCache.clear();
     if (m_unit) {
         const ClangString unitFile(clang_getTranslationUnitSpelling(unit));
         m_file = clang_getFile(m_unit, unitFile.c_str());
@@ -449,6 +450,8 @@
     // extra clang diagnostics
     const uint numDiagnostics = clang_getNumDiagnostics(d->m_unit);
     problems.reserve(numDiagnostics);
+    d->m_diagnosticsCache.resize(numDiagnostics);
+
     for (uint i = 0; i < numDiagnostics; ++i) {
         auto diagnostic = clang_getDiagnostic(d->m_unit, i);
 
@@ -461,7 +464,11 @@
             continue;
         }
 
-        ProblemPointer problem(ClangDiagnosticEvaluator::createProblem(diagnostic, d->m_unit));
+        auto& problem = d->m_diagnosticsCache[i];
+        if (!problem) {
+            problem = ClangDiagnosticEvaluator::createProblem(diagnostic, d->m_unit);
+        }
+
         problems << problem;
 
         clang_disposeDiagnostic(diagnostic);