diff --git a/src/cmd/compile/internal/gc/mpfloat.go b/src/cmd/compile/internal/gc/mpfloat.go
index b3a9af452ad..c1bbd3c1b49 100644
--- a/src/cmd/compile/internal/gc/mpfloat.go
+++ b/src/cmd/compile/internal/gc/mpfloat.go
@@ -183,15 +183,33 @@ func (a *Mpflt) SetString(as string) {
 	// TODO(gri) remove this code once math/big.Float.Parse can handle separators
 	as = strings.Replace(as, "_", "", -1) // strip separators
 
+	// TODO(gri) why is this needed?
 	for len(as) > 0 && (as[0] == ' ' || as[0] == '\t') {
 		as = as[1:]
 	}
 
-	f, _, err := a.Val.Parse(as, 0)
-	if err != nil {
-		yyerror("malformed constant: %s (%v)", as, err)
-		a.Val.SetFloat64(0)
-		return
+	// Currently, Val.Parse below (== math/big.Float.Parse) does not
+	// handle the 0o-octal prefix which can appear with octal integers
+	// with 'i' suffix, which end up here as imaginary components of
+	// complex numbers. Handle explicitly for now.
+	// TODO(gri) remove once Float.Parse can handle octals (it handles 0b/0B)
+	var f *big.Float
+	if strings.HasPrefix(as, "0o") || strings.HasPrefix(as, "0O") {
+		x, ok := new(big.Int).SetString(as[2:], 8)
+		if !ok {
+			yyerror("malformed constant: %s", as)
+			a.Val.SetFloat64(0)
+			return
+		}
+		f = a.Val.SetInt(x)
+	} else {
+		var err error
+		f, _, err = a.Val.Parse(as, 0)
+		if err != nil {
+			yyerror("malformed constant: %s (%v)", as, err)
+			a.Val.SetFloat64(0)
+			return
+		}
 	}
 
 	if f.IsInf() {
diff --git a/src/cmd/compile/internal/syntax/scanner.go b/src/cmd/compile/internal/syntax/scanner.go
index 0a77d48b3da..fbb3e1a40e6 100644
--- a/src/cmd/compile/internal/syntax/scanner.go
+++ b/src/cmd/compile/internal/syntax/scanner.go
@@ -512,9 +512,6 @@ func (s *scanner) number(c rune) {
 	// suffix 'i'
 	if c == 'i' {
 		s.kind = ImagLit
-		if prefix != 0 && prefix != '0' {
-			s.error("invalid suffix 'i' on " + litname(prefix))
-		}
 		c = s.getr()
 	}
 	s.ungetr()
diff --git a/src/cmd/compile/internal/syntax/scanner_test.go b/src/cmd/compile/internal/syntax/scanner_test.go
index 0f0579e2a5e..bfc44950bed 100644
--- a/src/cmd/compile/internal/syntax/scanner_test.go
+++ b/src/cmd/compile/internal/syntax/scanner_test.go
@@ -347,13 +347,14 @@ func TestNumbers(t *testing.T) {
 		{IntLit, "0b0190", "0b0190", "invalid digit '9' in binary literal"},
 		{IntLit, "0b01a0", "0b01 a0", ""}, // only accept 0-9
 
-		// binary floats and imaginaries (invalid)
 		{FloatLit, "0b.", "0b.", "invalid radix point in binary literal"},
 		{FloatLit, "0b.1", "0b.1", "invalid radix point in binary literal"},
 		{FloatLit, "0b1.0", "0b1.0", "invalid radix point in binary literal"},
 		{FloatLit, "0b1e10", "0b1e10", "'e' exponent requires decimal mantissa"},
 		{FloatLit, "0b1P-1", "0b1P-1", "'P' exponent requires hexadecimal mantissa"},
-		{ImagLit, "0b10i", "0b10i", "invalid suffix 'i' on binary literal"},
+
+		{ImagLit, "0b10i", "0b10i", ""},
+		{ImagLit, "0b10.0i", "0b10.0i", "invalid radix point in binary literal"},
 
 		// octals
 		{IntLit, "0o0", "0o0", ""},
@@ -365,13 +366,14 @@ func TestNumbers(t *testing.T) {
 		{IntLit, "0o1293", "0o1293", "invalid digit '9' in octal literal"},
 		{IntLit, "0o12a3", "0o12 a3", ""}, // only accept 0-9
 
-		// octal floats and imaginaries (invalid)
 		{FloatLit, "0o.", "0o.", "invalid radix point in octal literal"},
 		{FloatLit, "0o.2", "0o.2", "invalid radix point in octal literal"},
 		{FloatLit, "0o1.2", "0o1.2", "invalid radix point in octal literal"},
 		{FloatLit, "0o1E+2", "0o1E+2", "'E' exponent requires decimal mantissa"},
 		{FloatLit, "0o1p10", "0o1p10", "'p' exponent requires hexadecimal mantissa"},
-		{ImagLit, "0o10i", "0o10i", "invalid suffix 'i' on octal literal"},
+
+		{ImagLit, "0o10i", "0o10i", ""},
+		{ImagLit, "0o10e0i", "0o10e0i", "'e' exponent requires decimal mantissa"},
 
 		// 0-octals
 		{IntLit, "0", "0", ""},
@@ -389,6 +391,9 @@ func TestNumbers(t *testing.T) {
 
 		{IntLit, "1f", "1 f", ""}, // only accept 0-9
 
+		{ImagLit, "0i", "0i", ""},
+		{ImagLit, "0678i", "0678i", ""},
+
 		// decimal floats
 		{FloatLit, "0.", "0.", ""},
 		{FloatLit, "123.", "123.", ""},
@@ -424,7 +429,6 @@ func TestNumbers(t *testing.T) {
 		{FloatLit, "0p0", "0p0", "'p' exponent requires hexadecimal mantissa"},
 		{FloatLit, "1.0P-1", "1.0P-1", "'P' exponent requires hexadecimal mantissa"},
 
-		// decimal imaginaries
 		{ImagLit, "0.i", "0.i", ""},
 		{ImagLit, ".123i", ".123i", ""},
 		{ImagLit, "123.123i", "123.123i", ""},
@@ -441,6 +445,8 @@ func TestNumbers(t *testing.T) {
 		{IntLit, "0x", "0x", "hexadecimal literal has no digits"},
 		{IntLit, "0x1g", "0x1 g", ""},
 
+		{ImagLit, "0xf00i", "0xf00i", ""},
+
 		// hexadecimal floats
 		{FloatLit, "0x0p0", "0x0p0", ""},
 		{FloatLit, "0x12efp-123", "0x12efp-123", ""},
@@ -459,9 +465,7 @@ func TestNumbers(t *testing.T) {
 		{FloatLit, "0x1234PAB", "0x1234P AB", "exponent has no digits"},
 		{FloatLit, "0x1.2p1a", "0x1.2p1 a", ""},
 
-		// hexadecimal imaginaries (invalid)
-		{ImagLit, "0xf00i", "0xf00i", "invalid suffix 'i' on hexadecimal literal"},
-		{ImagLit, "0xf00.bap+12i", "0xf00.bap+12i", "invalid suffix 'i' on hexadecimal literal"},
+		{ImagLit, "0xf00.bap+12i", "0xf00.bap+12i", ""},
 
 		// separators
 		{IntLit, "0b_1000_0001", "0b_1000_0001", ""},
diff --git a/src/cmd/compile/internal/syntax/tokens.go b/src/cmd/compile/internal/syntax/tokens.go
index e00255a45e5..9b26c9f12f5 100644
--- a/src/cmd/compile/internal/syntax/tokens.go
+++ b/src/cmd/compile/internal/syntax/tokens.go
@@ -92,6 +92,9 @@ func contains(tokset uint64, tok token) bool {
 
 type LitKind uint
 
+// TODO(gri) With the 'i' (imaginary) suffix now permitted on integer
+//           and floating-point numbers, having a single ImagLit does
+//           not represent the literal kind well anymore. Remove it?
 const (
 	IntLit LitKind = iota
 	FloatLit
diff --git a/test/literal2.go b/test/literal2.go
index dbe22a012ed..f552e33adaf 100644
--- a/test/literal2.go
+++ b/test/literal2.go
@@ -5,7 +5,8 @@
 // license that can be found in the LICENSE file.
 
 // Test Go2 literal syntax for basic types.
-// TODO add more tests
+// Avoid running gofmt on this file to preserve the
+// test cases with upper-case prefixes (0B, 0O, 0X).
 
 package main
 
@@ -17,7 +18,7 @@ func assert(cond bool) {
 	}
 }
 
-func equal(x, y float64) bool {
+func equal(x, y interface{}) bool {
 	if x != y {
 		fmt.Printf("%g != %g\n", x, y)
 		return false
@@ -30,24 +31,30 @@ func main() {
 	assert(0_1 == 01)
 	assert(012 == 012)
 	assert(0_1_2 == 012)
+	assert(0_1_2i == complex(0, 12)) // decimal digits despite leading 0 for backward-compatibility
+	assert(00089i == complex(0, 89)) // decimal digits despite leading 0 for backward-compatibility
 
 	// decimals
 	assert(1_000_000 == 1000000)
+	assert(1_000i == complex(0, 1000))
 
 	// hexadecimals
 	assert(0x_1 == 0x1)
 	assert(0x1_2 == 0x12)
-	assert(0X_cafe_f00d == 0xcafef00d)
+	assert(0x_cafe_f00d == 0xcafef00d)
+	assert(0x_cafei == complex(0, 0xcafe))
 
 	// octals
 	assert(0o_1 == 01)
 	assert(0o12 == 012)
-	assert(0O_1_2 == 012)
+	assert(0o_1_2 == 012)
+	assert(0o_1_2i == complex(0, 0o12))
 
 	// binaries
 	assert(0b_1 == 1)
 	assert(0b10 == 2)
 	assert(0b_1_0 == 2)
+	assert(0b_1_0i == complex(0, 2))
 
 	// decimal floats
 	assert(0. == 0.0)
@@ -55,34 +62,29 @@ func main() {
 	assert(1_0. == 10.0)
 	assert(.0_1 == 0.01)
 	assert(1_0.0_1 == 10.01)
+	assert(1_0.0_1i == complex(0, 10.01))
 
 	assert(0.e1_0 == 0.0e10)
 	assert(.0e1_0 == 0.0e10)
 	assert(1_0.e1_0 == 10.0e10)
 	assert(.0_1e1_0 == 0.01e10)
 	assert(1_0.0_1e1_0 == 10.01e10)
+	assert(1_0.0_1e1_0i == complex(0, 10.01e10))
 
 	// hexadecimal floats
 	assert(equal(0x1p-2, 0.25))
 	assert(equal(0x2.p10, 2048.0))
 	assert(equal(0x1.Fp+0, 1.9375))
-	assert(equal(0X.8p-0, 0.5))
-	assert(equal(0X1FFFP-16, 0.1249847412109375))
+	assert(equal(0x.8p-0, 0.5))
+	assert(equal(0x1FFFp-16, 0.1249847412109375))
 	assert(equal(0x1.fffffffffffffp1023, 1.7976931348623157e308))
+	assert(equal(0x1.fffffffffffffp1023i, complex(0, 1.7976931348623157e308)))
 
 	assert(equal(0x_1p-2, 0.25))
 	assert(equal(0x2.p1_0, 2048.0))
 	assert(equal(0x1_0.Fp+0, 16.9375))
-	assert(equal(0X_0.8p-0, 0.5))
-	assert(equal(0X_1FF_FP-16, 0.1249847412109375))
-	assert(equal(0x1.f_ffff_ffff_ffffP1_023, 1.7976931348623157e308))
-
-	// imaginaries
-	assert(0i == complex(0, 0))
-	assert(09i == complex(0, 9)) // "09i" is a decimal int followed by "i"
-	assert(1.2e+3i == complex(0, 1.2e+3))
-
-	assert(0_0i == complex(0, 0))
-	assert(0_9i == complex(0, 9)) // "0_9i" is a decimal int followed by "i"
-	assert(1.2_0e+0_3i == complex(0, 1.2e+3))
+	assert(equal(0x_0.8p-0, 0.5))
+	assert(equal(0x_1FF_Fp-16, 0.1249847412109375))
+	assert(equal(0x1.f_ffff_ffff_ffffp1_023, 1.7976931348623157e308))
+	assert(equal(0x1.f_ffff_ffff_ffffp1_023i, complex(0, 1.7976931348623157e308)))
 }