Index: src/OFGZIPStream.h
==================================================================
--- src/OFGZIPStream.h
+++ src/OFGZIPStream.h
@@ -56,25 +56,25 @@
 		OF_GZIP_STREAM_FLAG_NAME	 = 0x08,
 		OF_GZIP_STREAM_FLAG_COMMENT	 = 0x10
 	} _flags;
 	uint8_t _extraFlags;
 	enum of_gzip_stream_os {
-		OF_GZIP_STREAM_OS_FAT	       =   0,
-		OF_GZIP_STREAM_OS_AMIGA	       =   1,
-		OF_GZIP_STREAM_OS_VMS	       =   2,
-		OF_GZIP_STREAM_OS_UNIX	       =   3,
-		OF_GZIP_STREAM_OS_VM_CMS       =   4,
-		OF_GZIP_STREAM_OS_ATARI_TOS    =   5,
-		OF_GZIP_STREAM_OS_HPFS	       =   6,
-		OF_GZIP_STREAM_OS_MACINTOSH    =   7,
-		OF_GZIP_STREAM_OS_Z_SYSTEM     =   8,
-		OF_GZIP_STREAM_OS_CP_M	       =   9,
-		OF_GZIP_STREAM_OS_TOPS_20      =  10,
-		OF_GZIP_STREAM_OS_NTFS	       =  11,
-		OF_GZIP_STREAM_OS_QDOS	       =  12,
-		OF_GZIP_STREAM_OS_ACORN_RISCOS =  13,
-		OF_GZIP_STREAM_OS_UNKNOWN      = 255
+		OF_GZIP_STREAM_OS_FAT		=   0,
+		OF_GZIP_STREAM_OS_AMIGA		=   1,
+		OF_GZIP_STREAM_OS_VMS		=   2,
+		OF_GZIP_STREAM_OS_UNIX		=   3,
+		OF_GZIP_STREAM_OS_VM_CMS	=   4,
+		OF_GZIP_STREAM_OS_ATARI_TOS	=   5,
+		OF_GZIP_STREAM_OS_HPFS		=   6,
+		OF_GZIP_STREAM_OS_MACINTOSH	=   7,
+		OF_GZIP_STREAM_OS_Z_SYSTEM	=   8,
+		OF_GZIP_STREAM_OS_CP_M		=   9,
+		OF_GZIP_STREAM_OS_TOPS_20	=  10,
+		OF_GZIP_STREAM_OS_NTFS		=  11,
+		OF_GZIP_STREAM_OS_QDO		=  12,
+		OF_GZIP_STREAM_OS_ACORN_RISC_OS	=  13,
+		OF_GZIP_STREAM_OS_UNKNOWN	= 255
 	} _OS;
 	size_t _bytesRead;
 	uint8_t _buffer[4];
 	OFDate *_Nullable _modificationDate;
 	uint16_t _extraLength;

Index: src/OFZIPArchiveEntry.h
==================================================================
--- src/OFZIPArchiveEntry.h
+++ src/OFZIPArchiveEntry.h
@@ -65,12 +65,12 @@
 	OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_WINDOWS_NTFS  = 10,
 	/*! MVS (OS/390 - Z/OS) */
 	OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_MVS	       = 11,
 	/*! VSE */
 	OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_VSE	       = 12,
-	/*! Acorn Risc */
-	OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_ACORN_RISC    = 13,
+	/*! Acorn RISC OS */
+	OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_ACORN_RISC_OS = 13,
 	/*! VFAT */
 	OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_VFAT	       = 14,
 	/*! Alternate MVS */
 	OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_ALTERNATE_MVS = 15,
 	/*! BeOS */

Index: src/OFZIPArchiveEntry.m
==================================================================
--- src/OFZIPArchiveEntry.m
+++ src/OFZIPArchiveEntry.m
@@ -74,12 +74,12 @@
 		attrCompat = "MVS (OS/390 - Z/OS)";
 		break;
 	case OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_VSE:
 		attrCompat = "VSE";
 		break;
-	case OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_ACORN_RISC:
-		attrCompat = "Acorn Risc";
+	case OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_ACORN_RISC_OS:
+		attrCompat = "Acorn RISC OS";
 		break;
 	case OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_VFAT:
 		attrCompat = "VFAT";
 		break;
 	case OF_ZIP_ARCHIVE_ENTRY_ATTR_COMPAT_ALTERNATE_MVS:

Index: src/platform.h
==================================================================
--- src/platform.h
+++ src/platform.h
@@ -89,13 +89,13 @@
 # endif
 # if defined(__mc68010__) || defined(OF_M68020)
 #  define OF_M68010
 # endif
 # if defined(__riscv) && defined(__riscv_xlen) && __riscv_xlen == 64
-#  define OF_RISCV64
+#  define OF_RISC_V_64
 # elif defined(__riscv)
-#  define OF_RISCV
+#  define OF_RISC_V
 # endif
 #endif
 
 #if defined(__APPLE__)
 # include <TargetConditionals.h>
@@ -141,10 +141,12 @@
 #elif defined(_PSP)
 # define OF_PSP
 #elif defined(__DJGPP__)
 # define OF_DJGPP
 # define OF_MSDOS
+#elif defined(__riscos__)
+# define OF_ACORN_RISC_OS
 #endif
 
 #if defined(__ELF__)
 # define OF_ELF
 #elif defined(__MACH__)