diff --git a/examples/upscale_cap.cpp b/examples/upscale_cap.cpp
index bc41986..ce18960 100644
--- a/examples/upscale_cap.cpp
+++ b/examples/upscale_cap.cpp
@@ -553,7 +553,7 @@ int main(int varnum, char** vararg)
        }
        
        // Check for saneness of Ptestvalue:
-       if (isnan(Ptestvalue) | isinf(Ptestvalue)) {
+       if (std::isnan(Ptestvalue) || std::isinf(Ptestvalue)) {
            cerr << "ERROR: Ptestvalue was inf or nan" << endl;
            break; // Jump out of while-loop, just print out the results
            // up to now and exit the program
diff --git a/examples/upscale_cond.cpp b/examples/upscale_cond.cpp
index 8ffe921..6bdbfee 100644
--- a/examples/upscale_cond.cpp
+++ b/examples/upscale_cond.cpp
@@ -713,7 +713,7 @@ int main(int varnum, char** vararg)
        }
        
        // Check for saneness of Ptestvalue:
-       if (isnan(Ptestvalue) | isinf(Ptestvalue)) {
+       if (std::isnan(Ptestvalue) || std::isinf(Ptestvalue)) {
            if (isMaster) cerr << "ERROR: Ptestvalue was inf or nan" << endl;
            break; // Jump out of while-loop, just print out the results
            // up to now and exit the program
diff --git a/examples/upscale_relperm.cpp b/examples/upscale_relperm.cpp
index 7cf2e29..db4f73c 100644
--- a/examples/upscale_relperm.cpp
+++ b/examples/upscale_relperm.cpp
@@ -1187,7 +1187,7 @@ int main(int varnum, char** vararg)
        }
        
        // Check for saneness of Ptestvalue:
-       if (isnan(Ptestvalue) | isinf(Ptestvalue)) {
+       if (std::isnan(Ptestvalue) || std::isinf(Ptestvalue)) {
            if (isMaster) cerr << "ERROR: Ptestvalue was inf or nan" << endl;
            break; // Jump out of while-loop, just print out the results
            // up to now and exit the program
diff --git a/examples/upscale_relpermvisc.cpp b/examples/upscale_relpermvisc.cpp
index 4d1c6f8..4d974cb 100644
--- a/examples/upscale_relpermvisc.cpp
+++ b/examples/upscale_relpermvisc.cpp
@@ -1081,7 +1081,7 @@ int main(int varnum, char** vararg)
         }
             
         // Check for saneness of fracFlowRatioTestvalue
-        if (isnan(fracFlowRatioTestvalue) || isinf(fracFlowRatioTestvalue)) {
+        if (std::isnan(fracFlowRatioTestvalue) || std::isinf(fracFlowRatioTestvalue)) {
             if (isMaster) cerr << "ERROR: fracFlowRatioTestvalue was inf or nan." << endl;
             break; // Jump out out while-loop, just print the results up to now and exit
         }