2 files changed, 2 insertions, 1 deletions
diff --git a/chapter21/src/test/java/com/seaofnodes/simple/TestC.java b/chapter21/src/test/java/com/seaofnodes/simple/TestC.java
index ce90c5fd..704cb5d4 100644
--- a/chapter21/src/test/java/com/seaofnodes/simple/TestC.java
+++ b/chapter21/src/test/java/com/seaofnodes/simple/TestC.java
@@ -44,6 +44,7 @@ public abstract class TestC {
         params.add("gcc");
         params.add(cfile);
         params.add(sofile);
+        params.add("-lm");
         params.add("-o");
         params.add(efile);
         Process gcc = new ProcessBuilder(params.toArray(String[]::new)).redirectErrorStream(true).start();
diff --git a/chapter21/src/test/java/com/seaofnodes/simple/progs/newtonFloat.c b/chapter21/src/test/java/com/seaofnodes/simple/progs/newtonFloat.c
index 25ac7930..70c9e426 100644
--- a/chapter21/src/test/java/com/seaofnodes/simple/progs/newtonFloat.c
+++ b/chapter21/src/test/java/com/seaofnodes/simple/progs/newtonFloat.c
@@ -7,7 +7,7 @@ extern double test_sqrt(double);
 int main( int argc, char** argv ) {
   double epsilon = 1e-50;
   for( int i=0; i<10; i++ ) {
-    double d = sqrt(i), expect = sqrt(i);
+    double d = test_sqrt(i), expect = sqrt(i);
     double delta = abs(d-expect);
     printf("%d  %f\n",i,d);
     if( delta > 1e-50 )