diff --git a/Pdf4QtLib/sources/pdfcolorconvertor.cpp b/Pdf4QtLib/sources/pdfcolorconvertor.cpp
index a85c8d9..785642f 100644
--- a/Pdf4QtLib/sources/pdfcolorconvertor.cpp
+++ b/Pdf4QtLib/sources/pdfcolorconvertor.cpp
@@ -174,7 +174,7 @@ float PDFColorConvertor::correctLigthnessBySigmoidFunction(float lightness) cons
 
 float PDFColorConvertor::sigmoidFunction(float value) const
 {
-    return 1.0f / (1.0f + std::expf(-m_sigmoidParamC * (value - 0.5f)));
+    return 1.0f / (1.0f + std::exp(-m_sigmoidParamC * (value - 0.5f)));
 }
 
 float PDFColorConvertor::sigmoidParamC_Black() const
diff --git a/Pdf4QtLib/sources/pdfimageconversion.cpp b/Pdf4QtLib/sources/pdfimageconversion.cpp
index 56c9952..14a9bb7 100644
--- a/Pdf4QtLib/sources/pdfimageconversion.cpp
+++ b/Pdf4QtLib/sources/pdfimageconversion.cpp
@@ -167,7 +167,7 @@ int PDFImageConversion::calculateOtsu1DThreshold() const
             u1 /= w1;
         }
 
-        const float variance = w0 * w1 * std::powf(u0 - u1, 2);
+        const float variance = w0 * w1 * std::pow(u0 - u1, 2);
         interClassVariance[i] = variance;
     }