diff --git a/src/tests/common-files/gnuplot_i.h b/src/tests/common-files/gnuplot_i.h
index 25ae7b681..614dc678e 100644
--- a/src/tests/common-files/gnuplot_i.h
+++ b/src/tests/common-files/gnuplot_i.h
@@ -247,7 +247,7 @@ public:
     Gnuplot& savetops(const std::string &filename = "gnuplot_output");
 
     /// saves a gnuplot session to a pdf file, filename without extension
-    Gnuplot& savetopdf(const std::string &filename = "gnuplot_output");
+    Gnuplot& savetopdf(const std::string &filename = "gnuplot_output", unsigned int font_size = 12);
 
     //----------------------------------------------------------------------------------
     // set and unset
@@ -1070,10 +1070,10 @@ Gnuplot& Gnuplot::showonscreen()
 //
 // saves a gnuplot session to a pdf file
 //
-Gnuplot& Gnuplot::savetopdf(const std::string &filename)
+Gnuplot& Gnuplot::savetopdf(const std::string &filename, unsigned int font_size)
 {
     std::ostringstream cmdstr;
-    cmdstr << "set term pdfcairo enhanced color font \"Times-New-Roman,18\"\n";
+    cmdstr << "set term pdfcairo enhanced color font \"Times-New-Roman," + std::to_string(font_size) + "\"\n";
     cmdstr << "set output \"" << filename << ".pdf\"\n";
     cmdstr << "replot";
     cmd(cmdstr.str());
diff --git a/src/tests/system-tests/position_test.cc b/src/tests/system-tests/position_test.cc
index c1705eca1..048abefea 100644
--- a/src/tests/system-tests/position_test.cc
+++ b/src/tests/system-tests/position_test.cc
@@ -617,7 +617,7 @@ void StaticPositionSystemTest::print_results(const std::vector<double> & east,
                     g1.cmd("replot");
 
                     g1.savetops("Position_test_2D");
-                    g1.savetopdf("Position_test_2D");
+                    g1.savetopdf("Position_test_2D", 18);
                     g1.showonscreen(); // window output
 
                     Gnuplot g2("points");
diff --git a/src/tests/unit-tests/arithmetic/fft_length_test.cc b/src/tests/unit-tests/arithmetic/fft_length_test.cc
index 0448fc114..f8ea83d22 100644
--- a/src/tests/unit-tests/arithmetic/fft_length_test.cc
+++ b/src/tests/unit-tests/arithmetic/fft_length_test.cc
@@ -126,7 +126,7 @@ TEST(FFTLengthTest, MeasureExecutionTime)
                             g1.plot_xy(fft_sizes_v, execution_times, "FFT execution time (averaged over " + std::to_string(FLAGS_fft_iterations_test) + " iterations)");
                             g1.set_style("points").plot_xy(powers_of_two, execution_times_powers_of_two, "Power of 2");
                             g1.savetops("FFT_execution_times_extended");
-                            g1.savetopdf("FFT_execution_times_extended");
+                            g1.savetopdf("FFT_execution_times_extended", 18);
                             g1.showonscreen(); // window output
 
                             Gnuplot g2("linespoints");
@@ -138,7 +138,7 @@ TEST(FFTLengthTest, MeasureExecutionTime)
                             g2.plot_xy(fft_sizes_v, execution_times, "FFT execution time (averaged over " + std::to_string(FLAGS_fft_iterations_test) + " iterations)");
                             g2.set_style("points").plot_xy(powers_of_two, execution_times_powers_of_two, "Power of 2");
                             g2.savetops("FFT_execution_times");
-                            g2.savetopdf("FFT_execution_times");
+                            g2.savetopdf("FFT_execution_times", 18);
                             g2.showonscreen(); // window output
                     }
                     catch (GnuplotException ge)