Index: uspace/lib/c/generic/strtol.c
===================================================================
--- uspace/lib/c/generic/strtol.c	(revision 31a566bc2fcd89f3a4bb7a0ed41cb3798eacac42)
+++ uspace/lib/c/generic/strtol.c	(revision 026003432853cb878c2eabd3af78ded8d7f01495)
@@ -77,6 +77,8 @@
 
 	if (nptr[1] == 'x' || nptr[1] == 'X') {
-		*nptrptr += 2;
-		return 16;
+		if (_digit_value(nptr[2]) < 16) {
+			*nptrptr += 2;
+			return 16;
+		}
 	}
 
@@ -85,16 +87,25 @@
 		case 'b':
 		case 'B':
-			*nptrptr += 2;
-			return 2;
+			if (_digit_value(nptr[2]) < 2) {
+				*nptrptr += 2;
+				return 2;
+			}
+			break;
 		case 'o':
 		case 'O':
-			*nptrptr += 2;
-			return 8;
+			if (_digit_value(nptr[2]) < 8) {
+				*nptrptr += 2;
+				return 8;
+			}
+			break;
 		case 'd':
 		case 'D':
 		case 't':
 		case 'T':
-			*nptrptr += 2;
-			return 10;
+			if (_digit_value(nptr[2]) < 10) {
+				*nptrptr += 2;
+				return 10;
+			}
+			break;
 		}
 	}
@@ -109,4 +120,6 @@
 	assert(nptr != NULL);
 	assert(sgn != NULL);
+
+	const char *first = nptr;
 
 	/* Skip leading whitespace. */
@@ -138,7 +151,10 @@
 		 * present when base is explicitly set to 16.
 		 * Our nonstandard str_* functions don't allow it.
+		 * I don't know if that is intended, just matching the original
+		 * functionality here.
 		 */
 
-		if (nptr[0] == '0' && (nptr[1] == 'x' || nptr[1] == 'X'))
+		if (nptr[0] == '0' && (nptr[1] == 'x' || nptr[1] == 'X') &&
+		    _digit_value(nptr[2]) < base)
 			nptr += 2;
 	}
@@ -149,5 +165,14 @@
 	}
 
-	/* Read the value. */
+	/* Must be at least one digit. */
+
+	if (_digit_value(*nptr) >= base) {
+		/* No digits on input. */
+		if (endptr != NULL)
+			*endptr = (char *) first;
+		return 0;
+	}
+
+	/* Read the value.  */
 
 	uintmax_t result = 0;
Index: uspace/lib/c/test/strtol.c
===================================================================
--- uspace/lib/c/test/strtol.c	(revision 31a566bc2fcd89f3a4bb7a0ed41cb3798eacac42)
+++ uspace/lib/c/test/strtol.c	(revision 026003432853cb878c2eabd3af78ded8d7f01495)
@@ -404,4 +404,11 @@
 	endp = endp_unchanged;
 	errno = errno_unchanged;
+	output = strtol(input = "    0xg", &endp, base = 0);
+	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
+	PCUT_ASSERT_PTR_EQUALS(input + 5, endp);
+	PCUT_ASSERT_INT_EQUALS(0, output);
+
+	endp = endp_unchanged;
+	errno = errno_unchanged;
 	output = strtol(input = "    0x1", &endp, base = 0);
 	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
@@ -418,8 +425,78 @@
 	endp = endp_unchanged;
 	errno = errno_unchanged;
+	output = strtol(input = "    0xg", &endp, base = 16);
+	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
+	PCUT_ASSERT_PTR_EQUALS(input + 5, endp);
+	PCUT_ASSERT_INT_EQUALS(0, output);
+
+	endp = endp_unchanged;
+	errno = errno_unchanged;
+	output = strtol(input = "    g", &endp, base = 16);
+	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
+	PCUT_ASSERT_PTR_EQUALS(input, endp);
+	PCUT_ASSERT_INT_EQUALS(0, output);
+
+	endp = endp_unchanged;
+	errno = errno_unchanged;
 	output = strtol(input = "    0x1", &endp, base = 16);
 	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
 	PCUT_ASSERT_PTR_EQUALS(input + 7, endp);
 	PCUT_ASSERT_INT_EQUALS(1, output);
+
+	endp = endp_unchanged;
+	errno = errno_unchanged;
+	output = strtol(input = "    +", &endp, base = 0);
+	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
+	PCUT_ASSERT_PTR_EQUALS(input, endp);
+	PCUT_ASSERT_INT_EQUALS(0, output);
+
+	endp = endp_unchanged;
+	errno = errno_unchanged;
+	output = strtol(input = "    -", &endp, base = 0);
+	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
+	PCUT_ASSERT_PTR_EQUALS(input, endp);
+	PCUT_ASSERT_INT_EQUALS(0, output);
+
+	endp = endp_unchanged;
+	errno = errno_unchanged;
+	output = strtol(input = "    +", &endp, base = 10);
+	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
+	PCUT_ASSERT_PTR_EQUALS(input, endp);
+	PCUT_ASSERT_INT_EQUALS(0, output);
+
+	endp = endp_unchanged;
+	errno = errno_unchanged;
+	output = strtol(input = "    -", &endp, base = 10);
+	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
+	PCUT_ASSERT_PTR_EQUALS(input, endp);
+	PCUT_ASSERT_INT_EQUALS(0, output);
+
+	endp = endp_unchanged;
+	errno = errno_unchanged;
+	output = strtol(input = "+", &endp, base = 0);
+	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
+	PCUT_ASSERT_PTR_EQUALS(input, endp);
+	PCUT_ASSERT_INT_EQUALS(0, output);
+
+	endp = endp_unchanged;
+	errno = errno_unchanged;
+	output = strtol(input = "-", &endp, base = 0);
+	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
+	PCUT_ASSERT_PTR_EQUALS(input, endp);
+	PCUT_ASSERT_INT_EQUALS(0, output);
+
+	endp = endp_unchanged;
+	errno = errno_unchanged;
+	output = strtol(input = "+", &endp, base = 10);
+	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
+	PCUT_ASSERT_PTR_EQUALS(input, endp);
+	PCUT_ASSERT_INT_EQUALS(0, output);
+
+	endp = endp_unchanged;
+	errno = errno_unchanged;
+	output = strtol(input = "-", &endp, base = 10);
+	PCUT_ASSERT_INT_EQUALS(errno_unchanged, errno);
+	PCUT_ASSERT_PTR_EQUALS(input, endp);
+	PCUT_ASSERT_INT_EQUALS(0, output);
 }