diff --git a/plugins/org.eclipse.mat.dtfj/.settings/org.eclipse.jdt.core.prefs b/plugins/org.eclipse.mat.dtfj/.settings/org.eclipse.jdt.core.prefs
index 1c52c693..69db5ab4 100644
--- a/plugins/org.eclipse.mat.dtfj/.settings/org.eclipse.jdt.core.prefs
+++ b/plugins/org.eclipse.mat.dtfj/.settings/org.eclipse.jdt.core.prefs
@@ -34,7 +34,7 @@ org.eclipse.jdt.core.compiler.problem.fatalOptionalError=disabled
 org.eclipse.jdt.core.compiler.problem.fieldHiding=ignore
 org.eclipse.jdt.core.compiler.problem.finalParameterBound=warning
 org.eclipse.jdt.core.compiler.problem.finallyBlockNotCompletingNormally=warning
-org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
+org.eclipse.jdt.core.compiler.problem.forbiddenReference=error
 org.eclipse.jdt.core.compiler.problem.hiddenCatchBlock=warning
 org.eclipse.jdt.core.compiler.problem.includeNullInfoFromAsserts=disabled
 org.eclipse.jdt.core.compiler.problem.incompatibleNonInheritedInterfaceMethod=warning
diff --git a/plugins/org.eclipse.mat.tests/.settings/org.eclipse.jdt.core.prefs b/plugins/org.eclipse.mat.tests/.settings/org.eclipse.jdt.core.prefs
index 1b858f81..e260d2a3 100644
--- a/plugins/org.eclipse.mat.tests/.settings/org.eclipse.jdt.core.prefs
+++ b/plugins/org.eclipse.mat.tests/.settings/org.eclipse.jdt.core.prefs
@@ -40,7 +40,7 @@ org.eclipse.jdt.core.compiler.problem.fatalOptionalError=disabled
 org.eclipse.jdt.core.compiler.problem.fieldHiding=ignore
 org.eclipse.jdt.core.compiler.problem.finalParameterBound=warning
 org.eclipse.jdt.core.compiler.problem.finallyBlockNotCompletingNormally=warning
-org.eclipse.jdt.core.compiler.problem.forbiddenReference=warning
+org.eclipse.jdt.core.compiler.problem.forbiddenReference=error
 org.eclipse.jdt.core.compiler.problem.hiddenCatchBlock=warning
 org.eclipse.jdt.core.compiler.problem.includeNullInfoFromAsserts=disabled
 org.eclipse.jdt.core.compiler.problem.incompatibleNonInheritedInterfaceMethod=warning