diff --git a/eo/app/gpsymreg/fitness.h b/eo/app/gpsymreg/fitness.h
index 8f4b499d..e432b826 100644
--- a/eo/app/gpsymreg/fitness.h
+++ b/eo/app/gpsymreg/fitness.h
@@ -203,10 +203,13 @@ class RegFitness: public eoEvalFunc< eoParseTree<FType, TreeNode> >
 					fit += pow(target - output, 2);
 				}
 				// check if the fitness is valid
+				// some versions of gcc (e.g. 2.95.2 on solaris) don't have isinf(x) defined
+				#ifdef isinf
 				if (isinf(fit) == 0)
 					fitness[NORMAL] = fit;
 				else
 					fitness[NORMAL] = MAXFLOAT;	
+				#endif
 				
 				fitness[SMALLESTSIZE] =  _eo.size() / (1.0*parameter.MaxSize);
 				_eo.fitness(fitness);
diff --git a/eo/app/gpsymreg/node.h b/eo/app/gpsymreg/node.h
index df10bd18..6905138c 100644
--- a/eo/app/gpsymreg/node.h
+++ b/eo/app/gpsymreg/node.h
@@ -161,8 +161,11 @@ class Node
 			}
 			
 			// if the result is infinite (positive or negative) or not_a_number (nan) then result becomes 0
+			// however some versions of gcc (e.g. 2.95.2 on solaris) don't have the finite(x) defined
+			#ifdef finite
 			if (!finite(result))
 				result=0;
+			#endif	
 		}
 		
 		template<class Children>