diff --git a/mex/build/matlab/mex.am b/mex/build/matlab/mex.am
index 0bd51ad0bf1f129903328bd25ff76a87fb7b732e..5e1c2b140d332b33a8010fecbf030ba415681e82 100644
--- a/mex/build/matlab/mex.am
+++ b/mex/build/matlab/mex.am
@@ -8,7 +8,7 @@ DEFS += -DMATLAB_MEX_FILE
 DEFS += -DMEXEXT=\"$(MEXEXT)\"
 
 AM_CFLAGS = $(MATLAB_CFLAGS) -Wall -Wno-parentheses
-AM_FCFLAGS = $(MATLAB_FCFLAGS) -Wall
+AM_FCFLAGS = $(MATLAB_FCFLAGS) -Wall -Wimplicit-interface
 AM_CXXFLAGS = $(MATLAB_CXXFLAGS) -Wall -Wno-parentheses -Wold-style-cast
 AM_LDFLAGS = $(MATLAB_LDFLAGS)
 LIBS += $(MATLAB_LIBS)
diff --git a/mex/build/octave/mex.am b/mex/build/octave/mex.am
index 4766d5d25f7344af4e008a729e6c91b5188be052..cb729355ea6f54a28951c3d1ed5f32c58a31557d 100644
--- a/mex/build/octave/mex.am
+++ b/mex/build/octave/mex.am
@@ -6,7 +6,7 @@ DEFS += -DOCTAVE_MEX_FILE
 DEFS += -DMEXEXT=\".mex\"
 
 AM_CFLAGS = $(shell $(MKOCTFILE) -p CPICFLAG) -Wall -Wno-parentheses
-AM_FCFLAGS = $(shell $(MKOCTFILE) -p FPICFLAG) -Wall
+AM_FCFLAGS = $(shell $(MKOCTFILE) -p FPICFLAG) -Wall -Wimplicit-interface
 AM_CXXFLAGS = $(shell $(MKOCTFILE) -p CXXPICFLAG) -Wall -Wno-parentheses -Wold-style-cast
 AM_LDFLAGS = $(shell $(MKOCTFILE) -p DL_LDFLAGS) -L"$(shell $(MKOCTFILE) -p OCTLIBDIR)"