diff --git a/src/plugins/cmakeprojectmanager/cmakeproject.cpp b/src/plugins/cmakeprojectmanager/cmakeproject.cpp
index ef10812ffdf..8942b98879a 100644
--- a/src/plugins/cmakeprojectmanager/cmakeproject.cpp
+++ b/src/plugins/cmakeprojectmanager/cmakeproject.cpp
@@ -177,7 +177,7 @@ void CMakeProject::changeBuildDirectory(CMakeBuildConfiguration *bc, const QStri
     parseCMakeLists();
 }
 
-QStringList CMakeProject::getCXXFlagsFor(const CMakeBuildTarget &buildTarget)
+QStringList CMakeProject::getCXXFlagsFor(const CMakeBuildTarget &buildTarget, QByteArray *cachedBuildNinja)
 {
     QString makeCommand = QDir::fromNativeSeparators(buildTarget.makeCommand);
     int startIndex = makeCommand.indexOf(QLatin1Char('\"'));
@@ -206,32 +206,43 @@ QStringList CMakeProject::getCXXFlagsFor(const CMakeBuildTarget &buildTarget)
     // found
     // Get "all" target's working directory
     if (!buildTargets().empty()) {
-        QString buildNinjaFile = QDir::fromNativeSeparators(buildTargets().at(0).workingDirectory);
-        buildNinjaFile += QLatin1String("/build.ninja");
-        QFile buildNinja(buildNinjaFile);
-        if (buildNinja.exists()) {
-            buildNinja.open(QIODevice::ReadOnly | QIODevice::Text);
-            QTextStream stream(&buildNinja);
-            bool targetFound = false;
-            bool cxxFound = false;
-            QString targetSearchPattern = QString::fromLatin1("target %1").arg(buildTarget.title);
-
-            while (!stream.atEnd()) {
-                // 1. Look for a block that refers to the current target
-                // 2. Look for a build rule which invokes CXX_COMPILER
-                // 3. Return the FLAGS definition
-                QString line = stream.readLine().trimmed();
-                if (line.startsWith(QLatin1String("#"))) {
-                    if (!line.startsWith(QLatin1String("# Object build statements for"))) continue;
-                    targetFound = line.endsWith(targetSearchPattern);
-                } else if (targetFound && line.startsWith(QLatin1String("build"))) {
-                    cxxFound = line.indexOf(QLatin1String("CXX_COMPILER")) != -1;
-                } else if (cxxFound && line.startsWith(QLatin1String("FLAGS ="))) {
-                    // Skip past =
-                    return line.mid(7).trimmed().split(QLatin1Char(' '), QString::SkipEmptyParts);
-                }
+        if (cachedBuildNinja->isNull()) {
+            QString buildNinjaFile = QDir::fromNativeSeparators(buildTargets().at(0).workingDirectory);
+            buildNinjaFile += QLatin1String("/build.ninja");
+            QFile buildNinja(buildNinjaFile);
+            if (buildNinja.exists()) {
+                buildNinja.open(QIODevice::ReadOnly | QIODevice::Text);
+                *cachedBuildNinja = buildNinja.readAll();
+                buildNinja.close();
+            } else {
+                *cachedBuildNinja = QByteArray();
             }
         }
+
+        if (cachedBuildNinja->isEmpty())
+            return QStringList();
+
+        QTextStream stream(cachedBuildNinja);
+        bool targetFound = false;
+        bool cxxFound = false;
+        QString targetSearchPattern = QString::fromLatin1("target %1").arg(buildTarget.title);
+
+        while (!stream.atEnd()) {
+            // 1. Look for a block that refers to the current target
+            // 2. Look for a build rule which invokes CXX_COMPILER
+            // 3. Return the FLAGS definition
+            QString line = stream.readLine().trimmed();
+            if (line.startsWith(QLatin1String("#"))) {
+                if (!line.startsWith(QLatin1String("# Object build statements for"))) continue;
+                targetFound = line.endsWith(targetSearchPattern);
+            } else if (targetFound && line.startsWith(QLatin1String("build"))) {
+                cxxFound = line.indexOf(QLatin1String("CXX_COMPILER")) != -1;
+            } else if (cxxFound && line.startsWith(QLatin1String("FLAGS ="))) {
+                // Skip past =
+                return line.mid(7).trimmed().split(QLatin1Char(' '), QString::SkipEmptyParts);
+            }
+        }
+
     }
     return QStringList();
 }
@@ -338,13 +349,15 @@ bool CMakeProject::parseCMakeLists()
 
     ppBuilder.setQtVersion(activeQtVersion);
 
+    QByteArray cachedBuildNinja;
     foreach (const CMakeBuildTarget &cbt, m_buildTargets) {
         // This explicitly adds -I. to the include paths
         QStringList includePaths = cbt.includeFiles;
         includePaths += projectDirectory().toString();
         ppBuilder.setIncludePaths(includePaths);
-        ppBuilder.setCFlags(getCXXFlagsFor(cbt));
-        ppBuilder.setCxxFlags(getCXXFlagsFor(cbt));
+        QStringList cxxflags = getCXXFlagsFor(cbt, &cachedBuildNinja);
+        ppBuilder.setCFlags(cxxflags);
+        ppBuilder.setCxxFlags(cxxflags);
         ppBuilder.setDefines(cbt.defines);
         ppBuilder.setDisplayName(cbt.title);
 
diff --git a/src/plugins/cmakeprojectmanager/cmakeproject.h b/src/plugins/cmakeprojectmanager/cmakeproject.h
index db58567df9b..ca35b9c7f08 100644
--- a/src/plugins/cmakeprojectmanager/cmakeproject.h
+++ b/src/plugins/cmakeprojectmanager/cmakeproject.h
@@ -139,7 +139,7 @@ private:
     QString uiHeaderFile(const QString &uiFile);
     void updateRunConfigurations(ProjectExplorer::Target *t);
     void updateApplicationAndDeploymentTargets();
-    QStringList getCXXFlagsFor(const CMakeBuildTarget &buildTarget);
+    QStringList getCXXFlagsFor(const CMakeBuildTarget &buildTarget, QByteArray *cachedBuildNinja);
 
     Internal::CMakeManager *m_manager;
     ProjectExplorer::Target *m_activeTarget;