diff --git a/python/plugins/processing/core/ProcessingConfig.py b/python/plugins/processing/core/ProcessingConfig.py
index a4fdba897ca..72254a87959 100644
--- a/python/plugins/processing/core/ProcessingConfig.py
+++ b/python/plugins/processing/core/ProcessingConfig.py
@@ -60,6 +60,7 @@ class ProcessingConfig(object):
     POST_EXECUTION_SCRIPT = 'POST_EXECUTION_SCRIPT'
     SHOW_CRS_DEF = 'SHOW_CRS_DEF'
     WARN_UNMATCHING_CRS = 'WARN_UNMATCHING_CRS'
+    WARN_UNMATCHING_EXTENT_CRS = 'WARN_UNMATCHING_EXTENT_CRS'
     DEFAULT_OUTPUT_RASTER_LAYER_EXT = 'DEFAULT_OUTPUT_RASTER_LAYER_EXT'
     DEFAULT_OUTPUT_VECTOR_LAYER_EXT = 'DEFAULT_OUTPUT_VECTOR_LAYER_EXT'
     SHOW_PROVIDERS_TOOLTIP = "SHOW_PROVIDERS_TOOLTIP"
@@ -108,6 +109,10 @@ class ProcessingConfig(object):
             ProcessingConfig.tr('General'),
             ProcessingConfig.WARN_UNMATCHING_CRS,
             ProcessingConfig.tr("Warn before executing if layer CRS's do not match"), True))
+        ProcessingConfig.addSetting(Setting(
+            ProcessingConfig.tr('General'),
+            ProcessingConfig.WARN_UNMATCHING_EXTENT_CRS,
+            ProcessingConfig.tr("Warn before executing if extent CRS might not match layers CRS"), True))
         ProcessingConfig.addSetting(Setting(
             ProcessingConfig.tr('General'),
             ProcessingConfig.RASTER_STYLE,
diff --git a/python/plugins/processing/gui/AlgorithmDialog.py b/python/plugins/processing/gui/AlgorithmDialog.py
index aa13eca8878..cc7e47b8b77 100644
--- a/python/plugins/processing/gui/AlgorithmDialog.py
+++ b/python/plugins/processing/gui/AlgorithmDialog.py
@@ -48,6 +48,9 @@ from processing.core.outputs import OutputVector
 from processing.core.outputs import OutputTable
 
 
+from qgis.utils import iface
+
+
 class AlgorithmDialog(AlgorithmDialogBase):
 
     def __init__(self, alg):
@@ -100,6 +103,37 @@ class AlgorithmDialog(AlgorithmDialogBase):
     def setParamValue(self, param, wrapper, alg=None):
         return param.setValue(wrapper.value())
 
+    def checkExtentCRS(self):
+        unmatchingCRS = False
+        hasExtent = False
+        projectCRS = iface.mapCanvas().mapSettings().destinationCrs()
+        layers = dataobjects.getAllLayers()
+        for param in self.alg.parameters:
+            if isinstance(param, (ParameterRaster, ParameterVector, ParameterMultipleInput)):
+                if param.value:
+                    if isinstance(param, ParameterMultipleInput):
+                        inputlayers = param.value.split(';')
+                    else:
+                        inputlayers = [param.value]
+                    for inputlayer in inputlayers:
+                        for layer in layers:
+                            if layer.source() == inputlayer:
+                                if layer.crs() != projectCRS:
+                                    unmatchingCRS = True
+
+                        p = dataobjects.getObjectFromUri(inputlayer)
+                        if p is not None:
+                            if p.crs() != projectCRS:
+                                unmatchingCRS = True
+            if isinstance(param, ParameterExtent):
+                value = self.mainWidget.valueItems[param.name].leText.text().strip()
+                print value
+                if value:
+                    hasExtent = True
+
+        return hasExtent and unmatchingCRS
+
+
     def accept(self):
         self.settings.setValue("/Processing/dialogBase", self.saveGeometry())
 
@@ -115,6 +149,17 @@ class AlgorithmDialog(AlgorithmDialogBase):
                                              QMessageBox.No)
                 if reply == QMessageBox.No:
                     return
+            checkExtentCRS = ProcessingConfig.getSetting(ProcessingConfig.WARN_UNMATCHING_EXTENT_CRS)
+            if checkExtentCRS and self.checkExtentCRS():
+                reply = QMessageBox.question(self, self.tr("Extent CRS"),
+                                             self.tr('Extent parameters must use the same CRS as the input layers.\n'
+                                                     'Your input layers do not have the same extent as the project, '
+                                                     'so the extent might be in a wrong CRS if you have selected it from the canvas.\n'
+                                                     'Do you want to continue?'),
+                                             QMessageBox.Yes | QMessageBox.No,
+                                             QMessageBox.No)
+                if reply == QMessageBox.No:
+                    return
             msg = self.alg._checkParameterValuesBeforeExecuting()
             if msg:
                 QMessageBox.warning(