diff --git a/src/Image.cpp b/src/Image.cpp
index 06f8cde86..a1c67a30a 100644
--- a/src/Image.cpp
+++ b/src/Image.cpp
@@ -31,7 +31,7 @@ template<UnsignedInt dimensions> void Image<dimensions>::setData(const typename
     _format = format;
     _type = type;
     _size = size;
-    _data = reinterpret_cast<char*>(data);
+    _data = reinterpret_cast<unsigned char*>(data);
 }
 
 template class Image<1>;
diff --git a/src/Image.h b/src/Image.h
index 37e4d80bd..f0de0ad67 100644
--- a/src/Image.h
+++ b/src/Image.h
@@ -55,7 +55,7 @@ template<UnsignedInt dimensions> class Image: public AbstractImage {
          * Note that the image data are not copied on construction, but they
          * are deleted on class destruction.
          */
-        inline explicit Image(const typename DimensionTraits<Dimensions, Int>::VectorType& size, Format format, Type type, GLvoid* data): AbstractImage(format, type), _size(size), _data(reinterpret_cast<char*>(data)) {}
+        inline explicit Image(const typename DimensionTraits<Dimensions, Int>::VectorType& size, Format format, Type type, GLvoid* data): AbstractImage(format, type), _size(size), _data(reinterpret_cast<unsigned char*>(data)) {}
 
         /**
          * @brief Constructor
@@ -74,8 +74,8 @@ template<UnsignedInt dimensions> class Image: public AbstractImage {
         inline typename DimensionTraits<Dimensions, Int>::VectorType size() const { return _size; }
 
         /** @brief Pointer to raw data */
-        inline void* data() { return _data; }
-        inline const void* data() const { return _data; } /**< @overload */
+        inline unsigned char* data() { return _data; }
+        inline const unsigned char* data() const { return _data; } /**< @overload */
 
         /**
          * @brief Set image data
@@ -91,7 +91,7 @@ template<UnsignedInt dimensions> class Image: public AbstractImage {
 
     private:
         Math::Vector<Dimensions, Int> _size;
-        char* _data;
+        unsigned char* _data;
 };
 
 #ifndef DOXYGEN_GENERATING_OUTPUT
diff --git a/src/ImageWrapper.h b/src/ImageWrapper.h
index 3a20cfc6c..e9e0b7f1d 100644
--- a/src/ImageWrapper.h
+++ b/src/ImageWrapper.h
@@ -62,7 +62,7 @@ template<UnsignedInt dimensions> class ImageWrapper: public AbstractImage {
          * Note that the image data are not copied on construction, but they
          * are deleted on class destruction.
          */
-        inline explicit ImageWrapper(const typename DimensionTraits<Dimensions, Int>::VectorType& size, Format format, Type type, GLvoid* data): AbstractImage(format, type), _size(size), _data(reinterpret_cast<char*>(data)) {}
+        inline explicit ImageWrapper(const typename DimensionTraits<Dimensions, Int>::VectorType& size, Format format, Type type, GLvoid* data): AbstractImage(format, type), _size(size), _data(reinterpret_cast<unsigned char*>(data)) {}
 
         /**
          * @brief Constructor
@@ -79,8 +79,8 @@ template<UnsignedInt dimensions> class ImageWrapper: public AbstractImage {
         inline typename DimensionTraits<Dimensions, Int>::VectorType size() const { return _size; }
 
         /** @brief Pointer to raw data */
-        inline void* data() { return _data; }
-        inline const void* data() const { return _data; } /**< @overload */
+        inline unsigned char* data() { return _data; }
+        inline const unsigned char* data() const { return _data; } /**< @overload */
 
         /**
          * @brief Set image data
@@ -91,12 +91,12 @@ template<UnsignedInt dimensions> class ImageWrapper: public AbstractImage {
          * destruction.
          */
         inline void setData(GLvoid* data) {
-            _data = reinterpret_cast<char*>(data);
+            _data = reinterpret_cast<unsigned char*>(data);
         }
 
     private:
         Math::Vector<Dimensions, Int> _size;
-        char* _data;
+        unsigned char* _data;
 };
 
 /** @brief One-dimensional image wrapper */
diff --git a/src/Trade/ImageData.h b/src/Trade/ImageData.h
index 8fd76c525..dbc6a548b 100644
--- a/src/Trade/ImageData.h
+++ b/src/Trade/ImageData.h
@@ -55,7 +55,7 @@ template<UnsignedInt dimensions> class ImageData: public AbstractImage {
          * Note that the image data are not copied on construction, but they
          * are deleted on class destruction.
          */
-        inline explicit ImageData(const typename DimensionTraits<Dimensions, Int>::VectorType& size, Format format, Type type, GLvoid* data): AbstractImage(format, type), _size(size), _data(reinterpret_cast<char*>(data)) {}
+        inline explicit ImageData(const typename DimensionTraits<Dimensions, Int>::VectorType& size, Format format, Type type, GLvoid* data): AbstractImage(format, type), _size(size), _data(reinterpret_cast<unsigned char*>(data)) {}
 
         /** @brief Destructor */
         inline ~ImageData() { delete[] _data; }
@@ -64,12 +64,12 @@ template<UnsignedInt dimensions> class ImageData: public AbstractImage {
         inline typename DimensionTraits<Dimensions, Int>::VectorType size() const { return _size; }
 
         /** @brief Pointer to raw data */
-        inline void* data() { return _data; }
-        inline const void* data() const { return _data; } /**< @overload */
+        inline unsigned char* data() { return _data; }
+        inline const unsigned char* data() const { return _data; } /**< @overload */
 
     private:
         Math::Vector<Dimensions, Int> _size;
-        char* _data;
+        unsigned char* _data;
 };
 
 /** @brief One-dimensional image */