diff --git a/src/asm/fstack.c b/src/asm/fstack.c
index b95f8640..14c63c1e 100644
--- a/src/asm/fstack.c
+++ b/src/asm/fstack.c
@@ -19,6 +19,7 @@
 #include "asm/main.h"
 #include "asm/symbol.h"
 #include "asm/warning.h"
+#include "error.h"
 #include "platform.h" // S_ISDIR (stat macro)
 
 #define MAXINCPATHS 128
@@ -137,7 +138,11 @@ void fstk_AddIncludePath(char const *path)
 
 void fstk_SetPreIncludeFile(char const *path)
 {
+	if (preIncludeName)
+		warnx("Overriding pre-included filename %s", preIncludeName);
 	preIncludeName = path;
+	if (verbose)
+		printf("Pre-included filename %s\n", preIncludeName);
 }
 
 static void printDep(char const *path)
diff --git a/src/asm/main.c b/src/asm/main.c
index 1f04c569..ad59fe9b 100644
--- a/src/asm/main.c
+++ b/src/asm/main.c
@@ -53,11 +53,11 @@ char const *__asan_default_options(void) { return "detect_leaks=0"; }
 // Unfortunately, macOS still ships 2.3, which is from 2008...
 int yyparse(void);
 
-FILE * dependfile;
-bool generatedMissingIncludes;
-bool failedOnMissingInclude;
-bool generatePhonyDeps;
-char *targetFileName;
+FILE *dependfile = NULL;
+bool generatedMissingIncludes = false;
+bool failedOnMissingInclude = false;
+bool generatePhonyDeps = false;
+char *targetFileName = NULL;
 
 bool haltnop;
 bool warnOnHaltNop;
@@ -148,9 +148,6 @@ static void print_usage(void)
 
 int main(int argc, char *argv[])
 {
-	int ch;
-	char *ep;
-
 	time_t now = time(NULL);
 	char const *sourceDateEpoch = getenv("SOURCE_DATE_EPOCH");
 
@@ -159,18 +156,11 @@ int main(int argc, char *argv[])
 	if (sourceDateEpoch)
 		now = (time_t)strtoul(sourceDateEpoch, NULL, 0);
 
-	dependfile = NULL;
-
 	// Perform some init for below
 	sym_Init(now);
 
 	// Set defaults
 
-	generatePhonyDeps = false;
-	generatedMissingIncludes = false;
-	failedOnMissingInclude = false;
-	targetFileName = NULL;
-
 	opt_B("01");
 	opt_G("0123");
 	opt_P(0);
@@ -183,8 +173,11 @@ int main(int argc, char *argv[])
 	warnings = true;
 	sym_SetExportAll(false);
 	uint32_t maxDepth = DEFAULT_MAX_DEPTH;
+	char *dependFileName = NULL;
 	size_t targetFileNameLen = 0;
 
+	int ch;
+	char *ep;
 	while ((ch = musl_getopt_long_only(argc, argv, optstring, longopts, NULL)) != -1) {
 		switch (ch) {
 		case 'b':
@@ -243,12 +236,17 @@ int main(int argc, char *argv[])
 			break;
 
 		case 'M':
-			if (!strcmp("-", musl_optarg))
+			if (dependfile)
+				warnx("Overriding dependfile %s", dependFileName);
+			if (!strcmp("-", musl_optarg)) {
 				dependfile = stdout;
-			else
+				dependFileName = "<stdout>";
+			} else {
 				dependfile = fopen(musl_optarg, "w");
+				dependFileName = musl_optarg;
+			}
 			if (dependfile == NULL)
-				err("Could not open dependfile %s", musl_optarg);
+				err("Could not open dependfile %s", dependFileName);
 			break;
 
 		case 'o':
diff --git a/src/asm/output.c b/src/asm/output.c
index d2725de2..4ca96bb7 100644
--- a/src/asm/output.c
+++ b/src/asm/output.c
@@ -540,7 +540,9 @@ void out_WriteObject(void)
 // Set the objectfilename
 void out_SetFileName(char *s)
 {
+	if (objectName)
+		warnx("Overriding output filename %s", objectName);
 	objectName = s;
 	if (verbose)
-		printf("Output filename %s\n", s);
+		printf("Output filename %s\n", objectName);
 }
diff --git a/src/gfx/main.cpp b/src/gfx/main.cpp
index ad974144..69e7dd67 100644
--- a/src/gfx/main.cpp
+++ b/src/gfx/main.cpp
@@ -337,6 +337,8 @@ static char *parseArgv(int argc, char **argv, bool &autoAttrmap, bool &autoTilem
 			break;
 		case 'a':
 			autoAttrmap = false;
+			if (!options.attrmap.empty())
+				warning("Overriding attrmap file %s", options.attrmap.c_str());
 			options.attrmap = musl_optarg;
 			break;
 		case 'b':
@@ -479,6 +481,8 @@ static char *parseArgv(int argc, char **argv, bool &autoAttrmap, bool &autoTilem
 			}
 			break;
 		case 'o':
+			if (!options.output.empty())
+				warning("Overriding tile data file %s", options.output.c_str());
 			options.output = musl_optarg;
 			break;
 		case 'P':
@@ -486,6 +490,8 @@ static char *parseArgv(int argc, char **argv, bool &autoAttrmap, bool &autoTilem
 			break;
 		case 'p':
 			autoPalettes = false;
+			if (!options.palettes.empty())
+				warning("Overriding palettes file %s", options.palettes.c_str());
 			options.palettes = musl_optarg;
 			break;
 		case 'Q':
@@ -493,6 +499,8 @@ static char *parseArgv(int argc, char **argv, bool &autoAttrmap, bool &autoTilem
 			break;
 		case 'q':
 			autoPalmap = false;
+			if (!options.palmap.empty())
+				warning("Overriding palette map file %s", options.palmap.c_str());
 			options.palmap = musl_optarg;
 			break;
 		case 'r':
@@ -520,6 +528,8 @@ static char *parseArgv(int argc, char **argv, bool &autoAttrmap, bool &autoTilem
 			break;
 		case 't':
 			autoTilemap = false;
+			if (!options.tilemap.empty())
+				warning("Overriding tilemap file %s", options.tilemap.c_str());
 			options.tilemap = musl_optarg;
 			break;
 		case 'V':
diff --git a/src/link/main.c b/src/link/main.c
index f162ad8b..30793e54 100644
--- a/src/link/main.c
+++ b/src/link/main.c
@@ -369,21 +369,31 @@ int main(int argc, char *argv[])
 			isWRA0Mode = true;
 			break;
 		case 'l':
+			if (linkerScriptName)
+				warnx("Overriding linkerscript %s", musl_optarg);
 			linkerScriptName = musl_optarg;
 			break;
 		case 'M':
 			noSymInMap = true;
 			break;
 		case 'm':
+			if (mapFileName)
+				warnx("Overriding mapfile %s", musl_optarg);
 			mapFileName = musl_optarg;
 			break;
 		case 'n':
+			if (symFileName)
+				warnx("Overriding symfile %s", musl_optarg);
 			symFileName = musl_optarg;
 			break;
 		case 'O':
+			if (overlayFileName)
+				warnx("Overriding overlay file %s", musl_optarg);
 			overlayFileName = musl_optarg;
 			break;
 		case 'o':
+			if (outputFileName)
+				warnx("Overriding output file %s", musl_optarg);
 			outputFileName = musl_optarg;
 			break;
 		case 'p':