diff --git a/gtsam/linear/GaussianFactor.h b/gtsam/linear/GaussianFactor.h
index 95364ea87..c8282e8b8 100644
--- a/gtsam/linear/GaussianFactor.h
+++ b/gtsam/linear/GaussianFactor.h
@@ -49,7 +49,7 @@ namespace gtsam {
 
     // Implementing Testable interface
     virtual void print(const std::string& s = "",
-        const IndexFormatter& formatter = DefaultIndexFormatter) const = 0;
+        const KeyFormatter& formatter = DefaultKeyFormatter) const = 0;
 
     /** Equals for testable */
     virtual bool equals(const GaussianFactor& lf, double tol = 1e-9) const = 0;
diff --git a/gtsam/linear/HessianFactor.h b/gtsam/linear/HessianFactor.h
index 2f0a2e1c4..895f31bc5 100644
--- a/gtsam/linear/HessianFactor.h
+++ b/gtsam/linear/HessianFactor.h
@@ -201,7 +201,7 @@ namespace gtsam {
 
     /** Print the factor for debugging and testing (implementing Testable) */
     virtual void print(const std::string& s = "",
-        const IndexFormatter& formatter = DefaultKeyFormatter) const;
+        const KeyFormatter& formatter = DefaultKeyFormatter) const;
 
     /** Compare to another factor for testing (implementing Testable) */
     virtual bool equals(const GaussianFactor& lf, double tol = 1e-9) const;