diff --git a/de4dot.code/FilesDeobfuscator.cs b/de4dot.code/FilesDeobfuscator.cs
index c972e69d..d6a5563e 100644
--- a/de4dot.code/FilesDeobfuscator.cs
+++ b/de4dot.code/FilesDeobfuscator.cs
@@ -268,7 +268,7 @@ namespace de4dot {
 					var inDir = Utils.getFullPath(searchDir.InputDirectory);
 					var outDir = Utils.getFullPath(searchDir.OutputDirectory);
 
-					if (!fileOptions.Filename.StartsWith(inDir, StringComparison.OrdinalIgnoreCase))
+					if (!Utils.StartsWith(fileOptions.Filename, inDir, StringComparison.OrdinalIgnoreCase))
 						throw new UserException(string.Format("Filename {0} does not start with inDir {1}", fileOptions.Filename, inDir));
 
 					var subDirs = fileOptions.Filename.Substring(inDir.Length);
diff --git a/de4dot.code/ObfuscatedFile.cs b/de4dot.code/ObfuscatedFile.cs
index 7010af03..99ef2565 100644
--- a/de4dot.code/ObfuscatedFile.cs
+++ b/de4dot.code/ObfuscatedFile.cs
@@ -326,7 +326,7 @@ namespace de4dot {
 
 			foreach (var val in options.StringDecrypterMethods) {
 				var tokenStr = val.Trim();
-				if (tokenStr.StartsWith("0x", StringComparison.OrdinalIgnoreCase))
+				if (Utils.StartsWith(tokenStr, "0x", StringComparison.OrdinalIgnoreCase))
 					tokenStr = tokenStr.Substring(2);
 				int methodToken;
 				if (int.TryParse(tokenStr, NumberStyles.HexNumber, null, out methodToken))
@@ -398,14 +398,14 @@ namespace de4dot {
 				remaining = "";
 			}
 
-			if (remaining.StartsWith("(", StringComparison.Ordinal)) {
+			if (Utils.StartsWith(remaining, "(", StringComparison.Ordinal)) {
 				stringArgs = remaining;
 			}
 			else if (remaining.Length > 0)
 				throw new UserException(string.Format("Invalid method desc: '{0}'", methodDesc));
 
 			if (stringArgs != null) {
-				if (stringArgs.StartsWith("(", StringComparison.Ordinal))
+				if (Utils.StartsWith(stringArgs, "(", StringComparison.Ordinal))
 					stringArgs = stringArgs.Substring(1);
 				if (stringArgs.EndsWith(")", StringComparison.Ordinal))
 					stringArgs = stringArgs.Substring(0, stringArgs.Length - 1);
diff --git a/de4dot.code/Utils.cs b/de4dot.code/Utils.cs
index dff2d724..65f7967d 100644
--- a/de4dot.code/Utils.cs
+++ b/de4dot.code/Utils.cs
@@ -183,5 +183,13 @@ namespace de4dot {
 			Log.log(logLevel, line);
 			Log.log(logLevel, "\n\nStack trace:\n{0}", ex.StackTrace);
 		}
+
+		// This fixes a mono (tested 2.10.5) String.StartsWith() bug. NB: stringComparison must be
+		// Ordinal or OrdinalIgnoreCase!
+		public static bool StartsWith(string left, string right, StringComparison stringComparison) {
+			if (left.Length < right.Length)
+				return false;
+			return left.Substring(0, right.Length).Equals(right, stringComparison);
+		}
 	}
 }
diff --git a/de4dot.code/deobfuscators/DeobfuscatorBase.cs b/de4dot.code/deobfuscators/DeobfuscatorBase.cs
index 478d717c..87959fee 100644
--- a/de4dot.code/deobfuscators/DeobfuscatorBase.cs
+++ b/de4dot.code/deobfuscators/DeobfuscatorBase.cs
@@ -398,7 +398,7 @@ namespace de4dot.deobfuscators {
 
 			foreach (var name in namesToPossiblyRemove) {
 				foreach (var moduleRef in module.ModuleReferences) {
-					if (moduleRef.Name.StartsWith(name, StringComparison.OrdinalIgnoreCase))
+					if (Utils.StartsWith(moduleRef.Name, name, StringComparison.OrdinalIgnoreCase))
 						addModuleReferenceToBeRemoved(moduleRef, reason);
 				}
 			}
diff --git a/de4dot.code/deobfuscators/SmartAssembly/Deobfuscator.cs b/de4dot.code/deobfuscators/SmartAssembly/Deobfuscator.cs
index cc23f29a..d38e60f9 100644
--- a/de4dot.code/deobfuscators/SmartAssembly/Deobfuscator.cs
+++ b/de4dot.code/deobfuscators/SmartAssembly/Deobfuscator.cs
@@ -142,7 +142,7 @@ namespace de4dot.deobfuscators.SmartAssembly {
 
 		void findSmartAssemblyAttributes() {
 			foreach (var type in module.Types) {
-				if (type.FullName.StartsWith("SmartAssembly.Attributes.PoweredByAttribute", StringComparison.Ordinal)) {
+				if (Utils.StartsWith(type.FullName, "SmartAssembly.Attributes.PoweredByAttribute", StringComparison.Ordinal)) {
 					foundSmartAssemblyAttribute = true;
 					addAttributeToBeRemoved(type, "Obfuscator attribute");
 					initializeVersion(type);
diff --git a/de4dot.code/renamer/Module.cs b/de4dot.code/renamer/Module.cs
index 369df002..daa184d4 100644
--- a/de4dot.code/renamer/Module.cs
+++ b/de4dot.code/renamer/Module.cs
@@ -78,7 +78,7 @@ namespace de4dot.renamer {
 		}
 
 		static string renameResourceString(string s, string oldTypeName, string newTypeName) {
-			if (!s.StartsWith(oldTypeName, StringComparison.Ordinal))
+			if (!Utils.StartsWith(s, oldTypeName, StringComparison.Ordinal))
 				return s;
 			if (s.Length == oldTypeName.Length)
 				return newTypeName;
@@ -152,7 +152,7 @@ namespace de4dot.renamer {
 
 					bool isValid = false;
 					foreach (var validName in validResourceNames) {
-						if (validName.StartsWith(oldName, StringComparison.Ordinal)) {
+						if (Utils.StartsWith(validName, oldName, StringComparison.Ordinal)) {
 							isValid = true;
 							break;
 						}