@@ -27,10 +27,12 @@
 #import "OFString.h"
 
 #ifdef _WIN32
 # include <windows.h>
 #endif
+
+OF_ASSUME_NONNULL_BEGIN
 
 @class OFArray OF_GENERIC(ObjectType);
 @class OFDictionary OF_GENERIC(KeyType, ObjectType);
 
 /*!
@@ -67,12 +69,13 @@
  * @param program The program to execute. If it does not start with a slash, the
  *		  search path specified in PATH is used.
  * @param arguments The arguments to pass to the program, or nil
  * @return A new, autoreleased OFProcess.
  */
-+ (instancetype)processWithProgram: (OFString*)program
-			 arguments: (OFArray OF_GENERIC(OFString*)*)arguments;
++ (instancetype)
+    processWithProgram: (OFString*)program
+	     arguments: (nullable OFArray OF_GENERIC(OFString*)*)arguments;
 
 /*!
  * @brief Creates a new OFProcess with the specified program, program name and
  *	  arguments and invokes the program.
  *
@@ -81,13 +84,14 @@
  * @param programName The program name for the program to invoke (argv[0]).
  *		      Usually, this is equal to program.
  * @param arguments The arguments to pass to the program, or nil
  * @return A new, autoreleased OFProcess.
  */
-+ (instancetype)processWithProgram: (OFString*)program
-		       programName: (OFString*)programName
-			 arguments: (OFArray OF_GENERIC(OFString*)*)arguments;
++ (instancetype)
+    processWithProgram: (OFString*)program
+	   programName: (OFString*)programName
+	     arguments: (nullable OFArray OF_GENERIC(OFString*)*)arguments;
 
 /*!
  * @brief Creates a new OFProcess with the specified program, program name,
  *	  arguments and environment and invokes the program.
  *
@@ -101,15 +105,16 @@
  *		      the environment. If you want to add to the existing
  *		      environment, you need to get the existing environment
  *		      first, copy it, modify it and then pass it.
  * @return A new, autoreleased OFProcess.
  */
-+ (instancetype)processWithProgram: (OFString*)program
-		       programName: (OFString*)programName
-			 arguments: (OFArray OF_GENERIC(OFString*)*)arguments
-		       environment: (OFDictionary OF_GENERIC(OFString*,
-					OFString*)*)environment;
++ (instancetype)
+    processWithProgram: (OFString*)program
+	   programName: (OFString*)programName
+	     arguments: (nullable OFArray OF_GENERIC(OFString*)*)arguments
+	   environment: (nullable OFDictionary
+			    OF_GENERIC(OFString*, OFString*)*)environment;
 
 /*!
  * @brief Initializes an already allocated OFProcess with the specified program
  *	  and invokes the program.
  *
@@ -127,11 +132,11 @@
  *		  search path specified in PATH is used.
  * @param arguments The arguments to pass to the program, or nil
  * @return An initialized OFProcess.
  */
 - initWithProgram: (OFString*)program
-	arguments: (OFArray OF_GENERIC(OFString*)*)arguments;
+	arguments: (nullable OFArray OF_GENERIC(OFString*)*)arguments;
 
 /*!
  * @brief Initializes an already allocated OFProcess with the specified program,
  *	  program name and arguments and invokes the program.
  *
@@ -142,11 +147,11 @@
  * @param arguments The arguments to pass to the program, or nil
  * @return An initialized OFProcess.
  */
 - initWithProgram: (OFString*)program
       programName: (OFString*)programName
-	arguments: (OFArray OF_GENERIC(OFString*)*)arguments;
+	arguments: (nullable OFArray OF_GENERIC(OFString*)*)arguments;
 
 /*!
  * @brief Initializes an already allocated OFProcess with the specified program,
  *	  program name, arguments and environment and invokes the program.
  *
@@ -162,12 +167,13 @@
  *		      first, copy it, modify it and then pass it.
  * @return An initialized OFProcess.
  */
 - initWithProgram: (OFString*)program
       programName: (OFString*)programName
-	arguments: (OFArray OF_GENERIC(OFString*)*)arguments
-      environment: (OFDictionary OF_GENERIC(OFString*, OFString*)*)environment;
+	arguments: (nullable OFArray OF_GENERIC(OFString*)*)arguments
+      environment: (nullable OFDictionary
+		       OF_GENERIC(OFString*, OFString*)*)environment;
 
 /*!
  * @brief Closes the write direction of the process.
  *
  * This method needs to be called for some programs before data can be read,
@@ -174,5 +180,7 @@
  * since some programs don't start processing before the write direction is
  * closed.
  */
 - (void)closeForWriting;
 @end
+
+OF_ASSUME_NONNULL_END