diff --git a/core/encoding/base64/base64.odin b/core/encoding/base64/base64.odin
index c1e2b6832..de764139d 100644
--- a/core/encoding/base64/base64.odin
+++ b/core/encoding/base64/base64.odin
@@ -533,5 +533,5 @@ decoded_len :: proc(data: string) -> int {
 		}
 	}
 
-	return ((length * 6) >> 3) - padding
+	return max(0, ((length * 6) >> 3) - padding)
 }
diff --git a/tests/issues/run.bat b/tests/issues/run.bat
index 1828604b5..151f0601b 100644
--- a/tests/issues/run.bat
+++ b/tests/issues/run.bat
@@ -103,6 +103,7 @@ clang -c ..\test_issue_sysv_abi.c -o test_issue_sysv_abi_c.o || exit /b
 ..\..\..\odin check ..\test_issue_poly_proc_value.odin %COMMON% 2>&1 | find /c "Error:" | findstr /x "4" || exit /b
 ..\..\..\odin test ..\test_issue_7779.odin %COMMON% || exit /b
 ..\..\..\odin run ..\test_issue_7798.odin %COMMON% || exit /b
+..\..\..\odin test ..\test_issue_7763.odin %COMMON% || exit /b
 ..\..\..\odin test ..\test_issue_disabled_proc_value.odin %COMMON% -disable-assert || exit /b
 
 @echo off
diff --git a/tests/issues/run.sh b/tests/issues/run.sh
index 6a13cce74..b379748f2 100755
--- a/tests/issues/run.sh
+++ b/tests/issues/run.sh
@@ -272,6 +272,7 @@ $ODIN test ../test_issue_7547.odin $COMMON -debug
 $ODIN test ../test_issue_7490.odin $COMMON
 $ODIN test ../test_issue_7779.odin $COMMON
 $ODIN run ../test_issue_7798.odin $COMMON
+$ODIN test ../test_issue_7763.odin $COMMON
 $ODIN test ../test_issue_disabled_proc_value.odin $COMMON -disable-assert
 
 set +x
diff --git a/tests/issues/test_issue_7763.odin b/tests/issues/test_issue_7763.odin
new file mode 100644
index 000000000..6428649ab
--- /dev/null
+++ b/tests/issues/test_issue_7763.odin
@@ -0,0 +1,151 @@
+package test_issues
+
+import "core:log"
+import "core:testing"
+import "core:encoding/base64"
+import "core:slice"
+import "core:strings"
+
+@(test)
+test_issue_7763__nothing :: proc(t: ^testing.T) {
+	input := ""
+	decoded, err := base64.decode(input)
+	testing.expect(t, err == nil)
+	testing.expect(t, decoded == nil)
+}
+
+@(test)
+test_issue_7763__1eq :: proc(t: ^testing.T) {
+	input := "="
+	decoded, err := base64.decode(input)
+	testing.expect(t, err == nil)
+	testing.expect(t, decoded == nil)
+}
+
+@(test)
+test_issue_7763__2eq :: proc(t: ^testing.T) {
+	input := "=="
+	decoded, err := base64.decode(input)
+	testing.expect(t, err == nil)
+	testing.expect(t, decoded == nil)
+}
+
+@(test)
+test_issue_7763__3eq :: proc(t: ^testing.T) {
+	for i in 3 ..= 8 {
+		input := strings.repeat("=", i, context.temp_allocator)
+		// NOTE: Error behavior is not well-defined at this point, but it should not crash and should return an empty slice.
+		decoded, err := base64.decode(input)
+		if err != nil {
+			log.infof("base64 decode %q yielded: %v", input, err)
+		}
+		testing.expect(t, decoded == nil)
+	}
+}
+
+@(test)
+test_issue_7763__Aeq :: proc(t: ^testing.T) {
+	input := "A="
+	decoded, err := base64.decode(input)
+	testing.expect(t, err == nil)
+	testing.expect(t, decoded == nil)
+}
+
+@(test)
+test_issue_7763__QQ :: proc(t: ^testing.T) {
+	input := "QQ"
+	decoded, err := base64.decode(input)
+	testing.expect(t, err == nil)
+	testing.expect(t, slice.equal(decoded, { 'A' }))
+	delete(decoded)
+}
+
+@(test)
+test_issue_7763__QQ1eq :: proc(t: ^testing.T) {
+	input := "QQ="
+	decoded, err := base64.decode(input)
+	testing.expect(t, err == nil)
+	testing.expect(t, slice.equal(decoded, { 'A' }))
+	delete(decoded)
+}
+
+@(test)
+test_issue_7763__QQ2eq :: proc(t: ^testing.T) {
+	input := "QQ=="
+	decoded, err := base64.decode(input)
+	testing.expect(t, err == nil)
+	testing.expect(t, slice.equal(decoded, { 'A' }))
+	delete(decoded)
+}
+
+@(test)
+test_issue_7763__QQ3eq :: proc(t: ^testing.T) {
+	for i in 3 ..= 8 {
+		// QQ====[...]
+		input := strings.concatenate({ "QQ", strings.repeat("=", i, context.temp_allocator) }, context.temp_allocator)
+		// NOTE: Error behavior is not well-defined at this point, but it should not crash, and in case it's successful, it should give 'A'.
+		decoded, err := base64.decode(input)
+		if err != nil {
+			log.infof("base64 decode %q yielded: %v", input, err)
+			testing.expect(t, decoded == nil)
+		} else {
+			testing.expect(t, decoded != nil)
+			delete(decoded)
+		}
+	}
+}
+
+// Strict
+
+@(test)
+test_issue_7763__strict_eq :: proc(t: ^testing.T) {
+	for i in 1 ..= 8 {
+		input := strings.repeat("=", i, context.temp_allocator)
+		decoded, err := base64.decode(input, options = { .Strict })
+		testing.expect_value(t, err, .Invalid_Padding)
+		testing.expect(t, decoded == nil)
+	}
+}
+
+@(test)
+test_issue_7763__strict_Aeq :: proc(t: ^testing.T) {
+	input := "A="
+	decoded, err := base64.decode(input, options = { .Strict })
+	testing.expect_value(t, err, .Invalid_Padding)
+	testing.expect(t, decoded == nil)
+}
+
+@(test)
+test_issue_7763__strict_QQ :: proc(t: ^testing.T) {
+	input := "QQ"
+	decoded, err := base64.decode(input, options = { .Strict })
+	testing.expect_value(t, err, .Invalid_Padding)
+	testing.expect(t, decoded == nil)
+}
+
+@(test)
+test_issue_7763__strict_QQ1eq :: proc(t: ^testing.T) {
+	input := "QQ="
+	decoded, err := base64.decode(input, options = { .Strict })
+	testing.expect_value(t, err, .Invalid_Padding)
+	testing.expect(t, decoded == nil)
+}
+
+@(test)
+test_issue_7763__strict_QQ2eq :: proc(t: ^testing.T) {
+	input := "QQ=="
+	decoded, err := base64.decode(input, options = { .Strict })
+	testing.expect(t, err == nil)
+	testing.expect(t, slice.equal(decoded, { 'A' }))
+	delete(decoded)
+}
+
+@(test)
+test_issue_7763__strict_QQ3eq :: proc(t: ^testing.T) {
+	for i in 3 ..= 8 {
+		input := strings.concatenate({ "QQ", strings.repeat("=", i, context.temp_allocator) }, context.temp_allocator)
+		decoded, err := base64.decode(input, options = { .Strict })
+		testing.expect_value(t, err, .Invalid_Padding)
+		testing.expect(t, decoded == nil)
+	}
+}