diff --git a/source/NVDAObjects/IAccessible/MSHTML.py b/source/NVDAObjects/IAccessible/MSHTML.py
index 634a2d7bf46..a2cb7b443a5 100644
--- a/source/NVDAObjects/IAccessible/MSHTML.py
+++ b/source/NVDAObjects/IAccessible/MSHTML.py
@@ -1139,7 +1139,7 @@ def findExtraIAccessibleOverlayClasses(obj, clsList):
 		clsList.append(MSAATextLeaf)
 		return
 
-	if iaRole == oleacc.ROLE_SYSTEM_WINDOW and obj.event_objectID > 0:
+	if iaRole == oleacc.ROLE_SYSTEM_WINDOW and obj.event_objectID is not None and obj.event_objectID > 0:
 		clsList.append(PluginWindow)
 	elif iaRole == oleacc.ROLE_SYSTEM_CLIENT and obj.event_objectID == winUser.OBJID_CLIENT:
 		clsList.append(RootClient)
diff --git a/source/NVDAObjects/IAccessible/adobeAcrobat.py b/source/NVDAObjects/IAccessible/adobeAcrobat.py
index a1563daff82..15acf0eefaa 100644
--- a/source/NVDAObjects/IAccessible/adobeAcrobat.py
+++ b/source/NVDAObjects/IAccessible/adobeAcrobat.py
@@ -39,7 +39,7 @@
 }
 
 def normalizeStdName(stdName):
-	if "H1" <= stdName <= "H6":
+	if stdName and "H1" <= stdName <= "H6":
 		return controlTypes.ROLE_HEADING, stdName[1]
 
 	try:
@@ -58,9 +58,9 @@ def initOverlayClass(self):
 			log.debugWarning("Could not get IServiceProvider")
 			return
 
-		if self.event_objectID > 0:
+		if self.event_objectID is not None and self.event_objectID > 0:
 			self.accID = self.event_objectID
-		elif self.event_childID > 0:
+		elif self.event_childID is not None and self.event_childID > 0:
 			self.accID = self.event_childID
 		else:
 			try:
diff --git a/source/braille.py b/source/braille.py
index c43de84de51..76344b437c5 100644
--- a/source/braille.py
+++ b/source/braille.py
@@ -480,8 +480,11 @@ def getBrailleTextForProperties(**propertyValues):
 	cellCoordsText=propertyValues.get('cellCoordsText')
 	rowNumber = propertyValues.get("rowNumber")
 	columnNumber = propertyValues.get("columnNumber")
-	rowSpan = propertyValues.get("rowSpan")
-	columnSpan = propertyValues.get("columnSpan")
+	# When fetching row and column span
+	# default the values to 1 to make further checks a lot simpler.
+	# After all, a table cell that has no rowspan implemented is assumed to span one row.
+	rowSpan = propertyValues.get("rowSpan") or 1
+	columnSpan = propertyValues.get("columnSpan") or 1
 	includeTableCellCoords = propertyValues.get("includeTableCellCoords", True)
 	if role is not None and not roleText:
 		if role == controlTypes.ROLE_HEADING and level:
diff --git a/source/virtualBuffers/adobeFlash.py b/source/virtualBuffers/adobeFlash.py
index a7f6c58bac4..91ec5b68a48 100644
--- a/source/virtualBuffers/adobeFlash.py
+++ b/source/virtualBuffers/adobeFlash.py
@@ -36,7 +36,7 @@ class AdobeFlash(VirtualBuffer):
 
 	def __init__(self,rootNVDAObject):
 		super(AdobeFlash,self).__init__(rootNVDAObject,backendName="adobeFlash")
-		self.isWindowless = rootNVDAObject.event_objectID > 0
+		self.isWindowless = rootNVDAObject.event_objectID is not None and rootNVDAObject.event_objectID > 0
 
 	def __contains__(self,obj):
 		if self.isWindowless: